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((short description|Hard keratin protection of digit))

((about|the anatomical features of primates' digits|the structure on some birds' beaks|Nail (beak)))

((redirect-multi|3|toenail|fingernail|paronychium|the construction technique|toenailing|the 2023 film|Fingernails (film)((!))''Fingernails'' (film)|parenchyme|parenchyma))

((anatomy terms))
((infobox anatomy
| Name        = Nail
| Latin       = unguis
| Width       = 160
| Image      = Fingernails2.jpg
| Caption    = Human fingernails
| Image2       = Blausen_0406_FingerNailAnatomy.png
| Caption2     = 
| Precursor   = 
| System      = [[Integumentary system]]
| Artery      = 
| Vein        = 
| Lymph       = 
))
A '''nail''' is a protective plate characteristically found at the tip of the [[digit (anatomy)|digit]]s ([[finger]]s and [[toe]]s) of all [[primate]]s, corresponding to the [[claw]]s in other [[tetrapod]] animals. Fingernails and toenails are made of a tough rigid [[protein]] called [[alpha-keratin]], a [[polymer]] also found in the claws, [[hooves]] and [[horn (anatomy)|horn]]s of [[vertebrate]]s.<ref name="Wang 2016">((Cite journal |last=Wang |first=Bin |title=Keratin: Structure, mechanical properties, occurrence in biological organisms, and efforts at bioinspiration |journal=Progress in Materials Science |volume=76 |pages=229–318 |year=2016 |doi=10.1016/j.pmatsci.2015.06.001|url=https://escholarship.org/content/qt5sb7q6jp/qt5sb7q6jp.pdf?t=o9xpu0 |doi-access=free ))</ref>

==Structure==
<!--((multiple image
| align     = right
| direction = vertical
| header    = Human nails
| width     = 200
| image1    = Fingernails2.jpg
| alt1      = Human fingers and nails
| caption1  = Fingernails
| image2    = Toes.png
| alt2      = Human toes and nails
| caption2  = Toenails
))-->
[[File:Human nail anatomy.jpg|thumb|left|A. Nail plate; B. lunula; C. root; D. sinus; E. matrix; F. nail bed; G. [[hyponychium]]; H. free margin.]]

The nail consists of the nail plate, the nail matrix and the nail bed below it, and the grooves surrounding it.<ref name="eMedicine">((cite web
 | url = http://emedicine.medscape.com/article/1126725-overview
 | title = Nail Surgery
 | first1 = Neh | last1 = Onumah
 | first2 = Richard K | last2 = Scher
 | publisher = eMedicine
 | date = May 2009 | access-date = 10 March 2010
))</ref>

=== Parts of the nail ===

The nail matrix is the active [[Tissue (biology)|tissue]] (or [[Germ layer|germinal]] [[Matrix (biology)|matrix]]) that generates cells. The cells harden as they move outward from the nail root to the nail plate.<ref name="Feneis-2000">((cite book
 | last        = Feneis
 | first       = Heinz
 | title       = Pocket Atlas of Human Anatomy
 | url         = https://archive.org/details/pocketatlashuman00fene_901
 | url-access  = 
 
 | year        = 2000
 | publisher   = Thieme
 | edition     = 4th
 | isbn        = 3-13-511204-7
 | pages       = [https://archive.org/details/pocketatlashuman00fene_901/page/n400 392]–95
))((dead link|date=September 2023))</ref> The nail matrix is also known as the ''matrix unguis'', keratogenous membrane, or onychostroma.<ref>((cite web
 | year        = 2005
 | title       = Nail matrix
 | url         = http://www.biology-online.org/dictionary/Nail_matrix
 | access-date = 10 March 2010
 | publisher   = Biology Online))</ref> It is the part of the nail bed that is beneath the nail and contains [[nerve]]s, [[lymph]] and [[blood vessel]]s. The matrix produces cells that become the nail plate. The width and thickness of the nail plate is determined by the size, length, and thickness of the matrix, while the shape of the fingertip bone determines if the nail plate is flat, arched, or hooked. The matrix will continue to produce cells as long as it receives nutrition and remains in a healthy condition.<ref>((Cite book
 | last        = D. Schoon
 | first       = Dougles
 | title       = Nail Structure and Products Chemistry
 | publisher   = Milady
 | year        = 2005
 | page        = 6
))</ref> As new nail plate cells are made, they push older nail plate cells forward; and in this way older cells become compressed, flat, and translucent. This makes the capillaries in the nail bed below visible, resulting in a pink color.((Citation needed|date=February 2021))

The [[Lunula (anatomy)|lunula]] ("small moon") is the visible part of the matrix, the whitish crescent-shaped base of the visible nail. The lunula can best be seen in the thumb and may not be visible in the little finger. The lunula appears white due to a reflection of light at the point where the nail matrix and nail bed meet.

((anchor|nail bed|bed))
The nail bed is the skin beneath the nail plate. It is the area of the nail on which the nail plate rests. Nerves and blood vessels found here supply nourishment to the entire nail unit. Like all skin, it is made of two types of tissues: the [[dermis]] and the [[Epidermis (skin)|epidermis]]. The epidermis is attached to the dermis by tiny longitudinal "grooves" called matrix crests (''cristae matricis unguis'').<ref name="Feneis-2000"/> In old age, the nail plate becomes thinner, and these grooves become more visible.((Citation needed|date=February 2021)) The nail bed is highly innervated, and removal of the nail plate is often excruciatingly painful as a result.((Citation needed|date=October 2022))

The nail sinus (''sinus unguis'') is where the nail root is;<ref name="Feneis-2000" /> i.e. the base of the nail underneath the skin. It originates from the actively growing tissue below, the matrix.((Citation needed|date=February 2021))

The nail plate (''corpus unguis'')<ref name="Feneis-2000" /> sometimes referred to as the nail body, is the visible hard nail area from the nail root to the free edge, made of translucent [[keratin]] protein. Several layers of dead, compacted cells cause the nail to be strong but flexible. Its (transverse) shape is determined by the form of the underlying bone.((Citation needed|date=February 2021)) In common usage, the word ''nail'' often refers to this part only. The nail plate is strongly attached to the nail bed and does not contain any nerves or blood vessels. 

The free margin (''margo liber'') or distal edge is the anterior margin of the nail plate corresponds to the abrasive or cutting edge of the nail.<ref name="Feneis-2000" />
The hyponychium (informally known as the "quick")<ref>((Cite book
 | last        = Crouch
 | first       = James Ensign
 | title       = Functional human anatomy
 | publisher   = Lea & Febiger
 | year        = 1985
 | page        = 80
 | url         = https://books.google.com/books?id=p8VqAAAAMAAJ&q=hyponychium+quick
 | isbn        = 9780812109306
 ))</ref> is the [[epithelium]] located beneath the nail plate at the junction between the free edge and the skin of the fingertip. It forms a seal that protects the nail bed. The onychodermal band is the seal between the nail plate and the hyponychium. It is just under the free edge, in that portion of the nail where the nail bed ends and can be recognized in fair-skinned people by its glassy, greyish colour. It is not visible in some individuals while it is highly prominent on others.((Citation needed|date=February 2021))

==== Eponychium ====

Together, the [[eponychium]] and the [[cuticle]] form a protective seal. The cuticle is the semi-circular layer of almost invisible dead skin cells that "ride out on" and cover the back of the visible nail plate. The eponychium is the fold of skin cells that produces the cuticle. They are continuous, and some references view them as one entity. (Thus the names ''eponychium'', ''cuticle'', and ''perionychium'' would be [[synonym]]ous,<ref name="Dorlands">((citation
 | author      = Elsevier
 | author-link = Elsevier
 | title       = Dorland's Illustrated Medical Dictionary
 | publisher   = Elsevier
 | url         = http://dorlands.com
 | postscript  = .
))</ref> although a distinction is still drawn here.) It is the cuticle (nonliving part) that is removed during a manicure, but the eponychium (living part) should not be touched due to risk of infection.((Citation needed|date=February 2021)) The [[eponychium]] is a small band of living cells ([[epithelium]]) that extends from the posterior nail wall onto the base of the nail.<ref name="Feneis-2000" /> The [[eponychium]] is ''the end'' of the proximal fold that folds back upon itself to shed an epidermal layer of skin onto the newly formed nail plate.((Contradict-inline|article=Cuticle|section=Human anatomy|date=October 2011)) The perionyx is the projecting edge of the eponychium covering the proximal strip of the lunula.<ref name="Feneis-2000" />

The nail wall (''vallum unguis'') is the cutaneous fold overlapping the sides and proximal end of the nail. The lateral margin (''margo lateralis'') lies beneath the nail wall on the sides of the nail, and the nail groove or fold (''sulcus matricis unguis'') are the cutaneous slits into which the lateral margins are embedded.<ref name="Feneis-2000" />

==== Paronychium ====

The paronychium is the soft tissue border around the nail,<ref name="Jordan-Mirzabeigi">((cite book
 | title       = Atlas of orthopaedic surgical exposures
 | first1      = Christopher
 | last1       = Jordan
 | first2      = Edwin
 | last2       = Mirzabeigi
 | publisher   = Thieme
 | isbn        = 0-86577-776-4
 | page        = 101
 | url         = https://books.google.com/books?id=gMSW59keA4UC&pg=PA101
 | date        = 2000-04-01
))</ref> and [[paronychia]] is an infection in this area.
The paronychium is the skin that overlaps onto the sides of the nail plate, also known as the paronychial edge. The paronychium is the site of hangnails, ingrown nails, and paronychia, a skin infection.

==== Hyponychium ====

The [[hyponychium]] is the area of epithelium, particularly the thickened portion, underlying the free edge of the nail plate. It is sometimes called the "quick", as in the phrase "cutting to the quick".

==Function==
A healthy fingernail has the function of protecting the [[Phalanx bone#Distal phalanx|distal phalanx]], the fingertip, and the surrounding soft tissues from injuries. It also serves to enhance precise delicate movements of the distal digits through counter-pressure exerted on the pulp of the finger.<ref name="eMedicine" />
The nail then acts as a counter-force when the end of the finger touches an object, thereby enhancing the sensitivity of the fingertip,<ref>((cite journal
 | url = http://www.aafp.org/afp/20010515/1961.html
 | title = Fingertip Injuries
 | first1 = Quincy C
 | last1 = Wang
 | first2 = Brett A
 | last2 = Johnson
 | journal = American Family Physician
 | date = May 2001
 | volume = 63
 | issue = 10
 | pages = 1961–6
 | pmid = 11388710
 | access-date = 10 March 2010
 | archive-date = 13 October 2008
 | archive-url = https://web.archive.org/web/20081013052327/http://www.aafp.org/afp/20010515/1961.html
 | url-status = dead
 ))</ref> although the nail itself has no nerve endings.
Finally, the nail functions as a tool enabling a so-called "extended precision grip" (e.g., pulling out a splinter in one's finger), and certain cutting or scraping actions.

===Growth===

The growing part of the nail is under the skin at the nail's [[Anatomical terms of location#Proximal and distal|proximal]] end under the [[Epidermis (skin)|epidermis]], which is the only living part of a nail.

In mammals, the growth rate of nails is related to the length of the terminal [[Phalanx (anatomy)|phalanges]] (outermost finger bones). Thus, in humans, the nail of the [[index finger]] grows faster than that of the little finger; and fingernails grow up to four times faster than toenails.<ref name="Ravosa-Dagosto-389">((cite book |doi=10.1007/978-0-387-33507-0_12 |chapter=Primate Gaits and Primate Origins |title=Primate Origins: Adaptations and Evolution |url=https://archive.org/details/primateoriginsad00ravo |url-access=limited |pages=[https://archive.org/details/primateoriginsad00ravo/page/n429 403]–35 |year=2007 |last1=Cartmill |first1=Matt |last2=Lemelin |first2=Pierre |last3=Schmitt |first3=Daniel |isbn=978-0-387-30335-2 |editor1-first=Matthew J. |editor1-last=Ravosa |editor2-first=Marian |editor2-last=Dagosto ))</ref>

In humans, fingernails grow at an average rate of approx. ((convert|3.5|mm|in|abbr=on)) a month, whereas toenails grow about half as fast (approx. average ((convert|1.6|mm|in|abbr=on)) a month).<ref>((Cite journal|last1=Yaemsiri|first1=S.|last2=Hou|first2=N.|last3=Slining|first3=M. M.|last4=He|first4=K.|date=2010|title=Growth rate of human fingernails and toenails in healthy American young adults|journal=Journal of the European Academy of Dermatology and Venereology|language=en|volume=24|issue=4|pages=420–423|doi=10.1111/j.1468-3083.2009.03426.x|pmid=19744178|s2cid=856692|issn=1468-3083))</ref> Fingernails require three to six months to regrow completely, and toenails require twelve to eighteen months. Actual growth rate is dependent upon age, sex, season, exercise level, diet, and [[hereditary]] factors.<ref>Hunter, J. A. A., Savin, J., & Dahl, M. V. (2002). ''Clinical dermatology''. Malden, Mass: Blackwell Science. p. 173. ((ISBN|0-632-05916-8))</ref> 
The longest female nails known ever to have existed measured a total of 8.65 m (28&nbsp;ft 4.5 in).<ref>"A nail-biting encounter with the woman who has the longest fingernails". Guinness World Records. 2019-11-04. Retrieved 2020-11-07.</ref> Contrary to popular belief, nails do not continue to grow after death; the skin [[dehydration|dehydrates]] and tightens, making the nails (and [[hair]]) appear to grow.<ref name="growth">((cite journal |doi=10.1136/bmj.39420.420370.25 |pmid=18156231 |pmc=2151163 |title=Medical myths |journal=BMJ |volume=335 |issue=7633 |pages=1288–9 |year=2007 |last1=Vreeman |first1=R. C |last2=Carroll |first2=A. E ))</ref>

===Permeability===
The nail is often considered an impermeable barrier, but this is not true. In fact, it is much more permeable than the skin,<ref name=penetration>[http://deepblue.lib.umich.edu/bitstream/2027.42/72442/1/j.1467-2494.1983.tb00348.x.pdf K. A. Walters and G. L. Flynn, Permeability characteristics of the human nail plate, International Journal of Cosmetic Science 5, 231–46 (1983)]</ref> and the composition of the nail includes 7–12% water. This permeability has implications for penetration by harmful and medicinal substances; in particular cosmetics applied to the nails can pose a risk. Water can penetrate the nail as can many other substances including [[paraquat]], a fast acting [[herbicide]] that is harmful to humans, [[urea]] which is often an ingredient in creams and lotions meant for use on hands and fingers, and several fungicidal agents such as [[salicylic acid]], [[miconazole]] branded Monistat, [[natamycin]]; and [[sodium hypochlorite]] which is the active ingredient in common household bleach (but usually only in 2–3% concentration).<ref name=penetration/>

==Clinical significance==
((Main|Nail disease))
[[File:Daumennagel mit Nagelhaut und Niednagel.jpg|thumb|Thumbnail of the right hand with [[cuticle]] (left) and [[hangnail]] (top)]]
Healthcare and pre-hospital-care providers ([[Emergency medical technician|EMT]]s or [[paramedic]]s) often use the fingernail beds as a cursory indicator of distal tissue [[perfusion]] of individuals who may be [[Dehydration|dehydrated]] or in [[Shock (circulatory)|shock]].<ref>[http://www.co.monterey.ca.us/health/EMS/pdfs/EMSManual.pdf Monterey County EMS Manual] ((Webarchive|url=https://web.archive.org/web/20081216214117/http://www.co.monterey.ca.us/health/EMS/pdfs/EMSManual.pdf |date=2008-12-16 )). Chapter XI, ''Patient assessment''.</ref> However, this test is not considered reliable in adults.<ref>((cite journal |author=Schriger DL, Baraff LJ |title=Capillary refill – is it a useful predictor of hypovolemic states? |journal=Ann Emerg Med |volume=20 |issue=6 |pages=601–15 |date=Jun 1991 |pmid=2039096 |doi=10.1016/S0196-0644(05)82375-3))</ref> This is known as the [[Capillary refill|CRT or blanch test]]. The fingernail bed is briefly depressed to turn the nail-bed white. When the pressure is released, the normal pink colour should be restored within a second or two. Delayed return to pink color can be an indicator of certain shock states such as [[hypovolemia]].<ref>((MedlinePlusEncyclopedia|003394|Capillary nail refill test))</ref><ref>[http://www.stlukes-stl.com/health-content/health-ency-multimedia/2/9154.htm St. Luke's Hospital]. Capillary nail refill test.</ref>

Nail growth record can show the history of recent health and physiological imbalances, and has been used as a [[diagnostic tool]] since ancient times.<ref>[https://www.aad.org/media/stats/prevention-and-care/nail-care American Academy of Dermatology – Nail Health]</ref><!--((ref|diagnoses))--> Deep, horizontally transverse grooves known as "[[Beau's lines]]" may form across the nails (horizontal, not along the nail from cuticle to tip). These lines are usually a natural consequence of aging, although they may result from disease. [[Chromonychia|Discoloration]], thinning, thickening, brittleness, splitting, grooves, [[Mees' lines]], [[leukonychia|small white spots]], receded lunula, [[Nail clubbing|clubbing]] (convex), flatness, and [[Choreic hand|spooning]] (concave) can indicate illness in other areas of the body, [[nutrient]] deficiencies, drug reaction or poisoning, or merely local injury.

Nails can also become thickened ([[onychogryphosis]]), loosened ([[onycholysis]]), infected with [[fungus]] ([[onychomycosis]]), or [[Degenerative disease|degenerate]] ([[onychodystrophy]]). A common nail disorder is an [[Ingrown nail|ingrowing toenail]] ([[onychocryptosis]]).

[[DNA profiling]] is a technique employed by [[forensic scientists]] on hair, fingernails, toenails, etc.

===Health and care===
[[File:Manicure kit late 1940s.jpg|150px|thumb|A set of professional nail care tools]]
The best way to care for nails is to trim them regularly. [[Nail file|Filing]] is also recommended, as to keep nails from becoming too rough and to remove any small bumps or ridges that may cause the nail to get tangled up in materials such as [[Textile|cloth]].<ref>((Cite journal|last1=Cohen|first1=Philip R.|last2=Scher|first2=Richard K.|date=1992-04-01|title=Geriatric nail disorders: Diagnosis and treatment|url=http://www.jaad.org/article/0190-9622(92)70075-Q/abstract|journal=Journal of the American Academy of Dermatology|language=en|volume=26|issue=4|pages=521–531|doi=10.1016/0190-9622(92)70075-Q|pmid=1597537|issn=0190-9622|doi-access=free))</ref>

Bluish or purple fingernail beds may be a symptom of peripheral [[cyanosis]], which indicates oxygen deprivation.

Nails can dry out, just like [[skin]]. They can also peel, break, and be [[Infection|infected]]. Toe infections, for instance, can be caused or exacerbated by [[dirty]] [[sock]]s, specific types of aggressive [[exercise]] ([[long-distance running]]), tight [[footwear]], and walking unprotected in an unclean [[Natural environment|environment]]. ((Citation needed|date=July 2007)) Common organisms causing nail infections include [[yeasts]] and [[Mold (fungus)|molds]] (particularly [[dermatophytes]]).<ref name="Denning">((cite journal|last=Denning|first=DW|author2=Evans, EG |author3=Kibbler, CC |author4=Richardson, MD |author5=Roberts, MM |author6=Rogers, TR |author7=Warnock, DW |author8= Warren, RE |date=November 11, 1995|title=Fungal nail disease: a guide to good practice (report of a Working Group of the British Society for Medical Mycology) |journal=[[British Medical Journal]]|volume=311|issue=7015|pages=1277–81|pmc=2551187 |pmid=7496239 |doi=10.1136/bmj.311.7015.1277))</ref>

Nail tools used by different people may transmit infections. Standard hygiene and sanitation procedures avoid transmission. In some cases, gel and cream cuticle removers can be used instead of cuticle scissors.
[[File:Human toenails.jpg|thumb|Human toenails]]

Nail disease can be very subtle and should be evaluated by a [[dermatologist]] with a focus in this particular area of medicine. However, most times it is a nail stylist who will note a subtle change in nail disease.

[[Inherited accessory nail of the fifth toe]] occurs where the toenail of the smallest toe is separated, forming a smaller "sixth toenail" in the outer corner of the nail.<ref name="Haneke_2016">((cite journal | vauthors = Haneke E | title = Double Nail of the Little Toe | journal = Skin Appendage Disorders | volume = 1 | issue = 4 | pages = 163–7 | date = May 2016 | pmid = 27386457 | pmc = 4908446 | doi = 10.1159/000443378 ))</ref> Like any other nail, it can be cut using a [[nail clipper]].

===Effect of nutrition===
Biotin-rich foods and supplements may help strengthen brittle fingernails.<ref name="ods">((cite web |title=Biotin |url=https://ods.od.nih.gov/factsheets/Biotin-HealthProfessional/ |publisher=Office of Dietary Supplements, US National Institutes of Health |access-date=15 July 2023 |date=10 January 2022))</ref>

[[Vitamin A]] is an essential micronutrient for vision, reproduction, cell and tissue differentiation, and immune function. [[Vitamin D]] and [[calcium]] work together in cases of maintaining homeostasis, creating muscle contraction, transmission of nerve pulses, blood clotting, and membrane structure. A lack of vitamin A, vitamin D, or calcium can cause dryness and brittleness.

Insufficient [[vitamin B12]] can lead to excessive dryness, darkened nails, and rounded or curved nail ends. Insufficient intake of both vitamin A and B results in fragile nails with horizontal and vertical ridges. Some over-the-counter vitamin supplements such as certain [[multivitamin]]s and [[biotin]] may help in growth of strong nails, although this is quite subjective. Both vitamin B12 and folate play a role in red blood cell production and oxygen transportation to nail cells. Inadequacies can result in discoloration of the nails.<ref>((cite journal |last1=Langan |first1=Robert C. |last2=Zawistoski |first2=Kimberly J. |title=Update on Vitamin B12 Deficiency |journal=American Family Physician |date=15 June 2011 |volume=83 |issue=12 |pages=1425–1430 |pmid=21671542 |url=https://www.aafp.org/link_out?pmid=21671542 ))</ref>

Diminished dietary intake of omega-3 fatty acids may contribute to dry and brittle nails.<ref>
((cite book
| title = Handbook of vitamins
| edition = 4th
| last = Zempleni
| first = J |author2=R.B. Rucker |author3=D.B. McCormick |author4=J.W. Suttie
| year = 2007
))((pn|date=June 2021))</ref>

[[Protein]] is a building material for new nails; therefore, low dietary protein intake may cause anemia and the resultant reduced hemoglobin in the blood filling the capillaries of the nail bed reflects varying amounts of light incident on the nail matrix resulting in lighter shades of pink ultimately resulting in white nail beds when the hemoglobin is very low. When hemoglobin is close to 15 or 16 grams, most of the spectrum of light is absorbed and only the pink color is reflected back and the nails look pink.

[[Essential fatty acids]] play a large role in healthy skin as well as nails. Splitting and flaking of nails may be due to a lack of [[linoleic acid]].

Iron-deficiency anemia can lead to a pale color along with a thin, brittle, ridged texture. Iron deficiency in general may cause the nails to become flat or concave, rather than convex. As oxygen is needed for healthy nails, an iron deficiency or anemia can lead to vertical ridges or concavity in the nails.<ref>((cite journal |last1=Singal |first1=Archana |last2=Arora |first2=Rahul |title=Nail as a window of systemic diseases |journal=Indian Dermatology Online Journal |date=2015 |volume=6 |issue=2 |pages=67–74 |doi=10.4103/2229-5178.153002 |pmid=25821724 |pmc=4375768 |doi-access=free ))</ref> RDAs for iron vary considerably depending on age and gender. The recommendation for men is 8&nbsp;mg per day, while that of women aged 19–50 is 18&nbsp;mg per day. After women hit age 50 or go through menopause, their iron needs drop to 8&nbsp;mg daily.<ref>((cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK56068/table/summarytables.t3/?report=objectonly|title = - Dietary Reference Intakes for Calcium and Vitamin D - NCBI Bookshelf|year = 2011))</ref><ref>
((cite journal
| author = Cashman MW, Sloan SB
| title = Nutrition and nail disease
| journal = Clinics in Dermatology
| volume = 28
| issue = 4
| pages = 420–25
| year = 2010
| pmid = 20620759
|doi = 10.1016/j.clindermatol.2010.03.037
))</ref>

==Society and culture==

===Fashion===
((main|manicure|pedicure))

[[File:Pedicure.JPG|250px|thumbnail|left|Toenails painted with magenta [[nail polish]]]]
Manicures (for the hands) and pedicures (for the feet) are health and cosmetic procedures to groom, trim, and paint the nails and manage [[callus]]es. They require various tools such as cuticle [[scissors]], nail scissors, [[nail clipper]]s, and [[nail file]]s. [[Artificial nails]] can also be fixed onto real nails for cosmetic purposes.

A person whose occupation is to cut, shape and care for nails as well as to apply overlays such as acrylic and UV gel is sometimes called a [[nail stylist]]. The place where a nail stylist works may be a [[nail salon]] or nail shop or nail bar.[[File:Nails and nature (17357450972).jpg|200px|thumb|Nail art]]

Acrylic nails are made out of acrylic glass (PMMA). When it is mixed with a liquid monomer (usually ethyl methacrylate mixed with some inhibitor) it forms a malleable bead. This mixture begins to cure immediately, continuing until completely solid in minutes. Acrylic nails can last up to 21 days but can last longer with touch-ups. To give acrylic nails color, gel polish, nail polish, and dip powders can be applied.<ref>((cite web |url=https://www.nailsmag.com/386817/secret-ingredient-acrylic-liquid|title=Secret Ingredient: Acrylic Liquid))</ref>

Painting the nails with colored [[nail polish]] (also called nail lacquer and nail varnish) to improve the appearance is a common practice dating back to at least 3000 B.C. 
Gel nails can be utilized in order to create artificial nail extensions, but can also be used like nail polish. They are hardened using ultraviolet light. They last longer than regular nail polish and do not chip. They have a high-gloss finish and last for two to three weeks.<ref>((cite web |url=https://www.huffingtonpost.co.uk/entry/are-gel-nails-damaging_uk_5d52b0bae4b05fa9df04c708|title=Gel Manicures Look Good, but What's the Damage to Your Nails?|date=12 October 2019))</ref>

Nail wraps are formed by cutting pieces of [[fiberglass]], linen, silk fabric, or another material to fit on the surface of the nail (or a tip attached prior), to be sealed onto the nail plate with a layer of resin or glue. They do not damage the nail and also provide strength to the nail but are not used to lengthen it. It can also be used to fix broken nails. The treatment is however more expensive.

With the dip powder method, a clear liquid is brushed onto a nail and the nail is then placed into pigmented powder.<ref>((cite web |url=https://www.glamour.com/story/dip-powder-nails-are-they-safe|title=Everything You Need to Know About Dip Powder Nails|date=3 January 2017))</ref> Dip nails tend to last about a month, 2–3 weeks longer than gel and acrylic nails.  It can be worn on natural nails, or with tips to create an artificial nail. Dip powder nails do not require any UV/LED light to be cured, instead they are sealed using an activator.((Citation needed|date=November 2021)) The quickest way to remove dip powder is to drill, clip off, or buff out layers of the powder so, when they are soaking in acetone, they slide right off.<ref>((cite book |url=https://books.google.com/books?id=qEO7daJsbCEC&pg=PA397|title = A Practical Guide to Beauty Therapy for NVQ Level 2|isbn = 9780748771509|last1 = Simms|first1 = Janet|year = 2003| publisher=Nelson Thornes ))</ref><ref>((cite web |url=https://www.allure.com/story/how-to-remove-dip-nails|title=How to Remove Dip Nails at Home|date=14 April 2020))</ref>

===Length records===

''[[Guinness World Records]]'' began tracking record fingernail lengths in 1955, when a Chinese priest was listed as having fingernails ((convert|1|ft|10.75|in|cm)) long.

The current record-holder for men, according to ''Guinness'', is [[Shridhar Chillal]] from India who set the record in 1998 with a total of ((convert|20|ft|2.25|in|cm)) of nails on his left hand. His longest nail, on his thumb, was ((convert|4|ft|9.6|in|cm)) long.

The record-holder for women is [[Lee Redmond]] of the U.S., who set the record in 2001 and as of 2008 had nails with a total length on both hands of ((convert|28|ft|cm)), with the longest nail on her right thumb at ((convert|2|ft|11|in|cm)).<ref name="msnbc.msn.com">((Cite news
 | title = Crash breaks woman's record-length fingernails
 | publisher = NBCNews | date = December 2009
 | url = http://www.nbcnews.com/id/29170772
))</ref>

==Evolution in primates==
[[File:PrimateFeet.jpg|thumb|left|Nails are a [[Primate#Distinguishing features|distinguishing feature]] of the primate order.]]
The nail is an ''[[unguis]]'', meaning a keratin structure at the end of a digit. Other examples of ''ungues'' include the claw, [[hoof]], and [[Claw#Birds|talon]]. The nails of [[primate]]s and the hooves of running mammals [[Evolution|evolved]] from the claws of [[synapsid|earlier animals]].<ref name=Ankel-Simons-2007>
((cite book
 | last = Ankel-Simons  | first = Friderun
 | date = 8 January 2007
 | title = Primate Anatomy: An introduction
 | edition = 3rd  | pages = 342–344
 | place = London, UK
 | publisher = Academic Press 
 | isbn = 978-0-12-372576-9
 | url = https://books.google.com/books?id=Mwl3M6c5KzoC&q=nail+OR+nails
))</ref>

In contrast to nails, claws are typically curved ventrally (downwards in animals) and compressed sideways. They serve a multitude of functions((mdash))including climbing, digging, and fighting((mdash))and have undergone numerous adaptive changes in different animal [[Taxon|taxa]]. Claws are pointed at their ends and are composed of two layers: a thick, deep layer and a superficial, hardened layer which serves a protective function. The underlying bone is a virtual mold of the overlying horny structure and therefore has the same shape as the claw or nail. Compared to claws, nails are flat, less curved, and do not extend far beyond the tip of the digits. The ends of the nails usually consist only of the "superficial", hardened layer and are not pointed like claws.<ref name=Ankel-Simons-2007/><!-- ref for para -->

With only a few exceptions, primates retain [[plesiomorphic]] (original, "primitive") hands with five digits, each equipped with either a nail or a claw. For example, nearly all living [[Strepsirrhini|strepsirrhine]] primates have nails on all digits except the second toe which is equipped with a [[grooming claw]]. [[Tarsier]]s have a grooming claw on second and third toes. Less commonly known, a grooming claw is also found on the second pedal digit of [[owl monkey]]s (''Aotus''), [[titi]]s (''Callicebus''), and possibly other [[New World monkey]]s.<ref name=Maiolino>
((Cite journal
 | last1 = Maiolino    | first1 = S.
 | last2 = Boyer       | first2 = D.M.
 | last3 = Rosenberger | first3 = A.
 | year = 2011
 | title = Morphological correlates of the grooming claw in distal phalanges of platyrrhines and other primates: A preliminary study
 | journal = The Anatomical Record
 | volume = 294  | issue = 12  | pages = 1975–1990
 | pmid=22042603  | s2cid = 3939930
 | doi = 10.1002/ar.21498 | doi-access = 
))
</ref> The [[needle-clawed bushbaby]] (''Euoticus'') has keeled nails (the thumb and the first and the second toes have claws) featuring a central ridge that ends in a needle-like tip.

A study of the fingertip morphology of four small-bodied [[New World monkey]] species indicated a correlation between increasing small-branch foraging and:
# expanded apical pads (fingertips),
# developed epidermal ridges ([[fingerprint]]s),
# broadened distal parts of [[distal phalanges]] (fingertip bones), and
# reduced flexor and extensor tubercles (attachment areas for finger muscles on bones).
This suggests that whereas claws are useful on large-diameter branches, wide fingertips with nails and epidermal ridges were required for habitual locomotion on small-diameter branches. It also indicates keel-shaped nails of ''[[Callitrichine]]s'' (a family of New World monkeys) is a derived postural adaptation rather than retained ancestral condition.<ref>
((cite journal
 | last = Hamrick  | first = Mark W.
 | year = 1998
 | title = Functional and adaptive significance of primate pads and claws: Evidence from New World anthropoids
 | journal = American Journal of Physical Anthropology
 | volume = 106  | issue = 2  | pages = 113–27
 | publisher = Wiley-Liss
 | pmid = 9637179
 | doi = 10.1002/(SICI)1096-8644(199806)106:2<113::AID-AJPA2>3.0.CO;2-R
))</ref>

==See also==
*[[List of cutaneous conditions]]
*[[Nail disease]]
*[[Foot fetishism]]
*[[Hand fetishism]]
*[[Onychogryphosis]], overgrown, claw-like nails

==References==
((Reflist|30em))

* ((Commonscatinline|Nails))

((Human regional anatomy))
((Integumentary system))
((Authority control))

((DEFAULTSORT:Nail (Anatomy)))
[[Category:Nails (anatomy)| ]]

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