Between five and six million people use Tok Pisin to some degree, although not all speak it fluently. Many now learn it as a first language, in particular the children of parents or grandparents who originally spoke different languages (for example, a mother from Madang and a father from Rabaul). Urban families in particular, and those of police and defence force members, often communicate among themselves in Tok Pisin, either never gaining fluency in a local language (tok ples) or learning a local language as a second (or third) language, after Tok Pisin (and possibly English). Over the decades, Tok Pisin has increasingly overtaken Hiri Motu as the dominant lingua franca among town-dwellers. Perhaps one million people now use Tok Pisin as a primary language. Tok Pisin is slowly "crowding out" other languages of Papua New Guinea.
A 1971 reference book on Tok Pisin (referring to the language as Melanesian Pidgin).
Hotel room door signs in Papua New Guinea
Tok is derived from English "talk", but has a wider application, also meaning "word", "speech", or "language". Pisin derives from the English word 'pidgin'; the latter, in turn, may originate in the word business, which is descriptive of the typical development and use of pidgins as inter-ethnic trade languages.
While Tok Pisin's name in the language is Tok Pisin, it is also called "New Guinea Pidgin" in English. Papua New Guinean anglophones often refer to Tok Pisin as "Pidgin" when speaking English. This usage of "Pidgin" differs from the term "pidgin" as used in linguistics. Tok Pisin is not a pidgin in the latter sense, since it has become a first language for many people (rather than simply a lingua franca to facilitate communication with speakers of other languages). As such, it is considered a creole in linguistic terminology.
This English-based pidgin evolved into Tok Pisin in German New Guinea (where the German-based creole Unserdeutsch was also spoken). It became a widely used lingua franca and language of interaction between rulers and ruled, and among the ruled themselves who did not share a common vernacular. Tok Pisin and the closely related Bislama in Vanuatu and Pijin in the Solomon Islands, which developed in parallel, have traditionally been treated as varieties of a single Melanesian Pidgin English or "Neo-Melanesian" language. The flourishing of the mainly English-based Tok Pisin in German New Guinea (despite the language of the metropolitan power being German) is to be contrasted with Hiri Motu, the lingua franca of Papua, which was derived not from English but from Motu, the vernacular of the indigenous people of the Port Moresby area.
Along with English and Hiri Motu, Tok Pisin is one of the three official languages of Papua New Guinea. It is frequently the language of debate in the national parliament. Most government documents are produced in English, but public information campaigns are often partially or entirely in Tok Pisin. While English is the main language in the education system, some schools use Tok Pisin in the first three years of elementary education to promote early literacy.
There are considerable variations in vocabulary and grammar in various parts of Papua New Guinea, with distinct dialects in the New Guinea Highlands, the north coast of Papua New Guinea, and islands outside of New Guinea. For example, Pidgin speakers from Finschhafen speak rather quickly and often have difficulty making themselves understood elsewhere. The variant spoken on Bougainville and Buka is moderately distinct from that of New Ireland and East New Britain but is much closer to that than it is to the Pijin spoken in the rest of the Solomon Islands.
There are 4 sociolects of Tok Pisin: Tok Bus (meaning "talk of the remote areas") or Tok Kanaka (meaning "talk of the people of the remote areas"), Tok Bilong Asples (meaning "language of the villages") which is the traditional rural Tok Pisin, Tok Skul (meaning "talk of the schools") or Tok Bilong Taun (meaning "talk of the Towns") which is the urban Tok Pisin, and Tok Masta (meaning "language of the colonizers"). 
The Tok Pisin alphabet contains 22 letters, five of which are vowels, and four digraphs. The letters are (vowels in bold):
a, b, d, e, f, g, h, i, k, l, m, n, o, p, r, s, t, u, v, w, y
The four digraphs note diphthongs, as well as certain consonants:
⟨ai⟩, ⟨au⟩, ⟨oi⟩ and ⟨ng⟩ (used for both /ŋ/ and /ŋɡ/)
Tok Pisin, like many pidgins and creoles, has a simpler phonology than the superstrate language. It has 17 consonants and 5 vowels. However, this varies with the local substrate languages and the level of education of the speaker. The following is the "core" phonemic inventory, common to virtually all varieties of Tok Pisin. More educated speakers, and/or those where the substrate language(s) have larger phoneme inventories, may have as many as 10 distinct vowels.
The verb has a suffix, -im (< Eng. him) to indicate transitivity (luk, "look"; lukim, "see"). But some verbs, such as kaikai "eat", can be transitive without it. Tense is indicated by the separate words bai Future (< Eng. by and by) and bin (past) (< Eng. been). The present progressive tense is indicated by the word stap – e.g. Hem kaikai stap "He is eating".
The noun does not indicate number, though pronouns do.
Adjectives usually take the suffix -pela (now often pronounced -pla, though more so for pronouns, and -pela for adjectives; from "fellow") when modifying nouns; an exception is liklik "little". It is also found on numerals and determiners:
the genitive preposition bilong (etym. < Eng. belong), which is equivalent to "of", "from" and some uses of "for": e.g. Ki bilong yu "your key"; Ol bilong Godons "They are from Gordon's".
the oblique preposition long (etym. < Eng. along), which is used for various other relations (such as locative or dative): e.g. Mipela i bin go long blekmaket. "We went to the black market".
Some phrases are used as prepositions, such as long namel (bilong), "in the middle of".
Several of these features derive from the common grammatical norms of Austronesian languages – although usually in a simplified form. Other features, such as word order, are however closer to English.
Sentences which have a 3rd person subject often put the word i immediately before the verb. This may or may not be written separate from the verb, occasionally written as a prefix. Although the word is thought to be derived from "he" or "is", it is not itself a pronoun or a verb but a grammatical marker used in particular constructions, e.g., Kar i tambu long hia is "car forbidden here", i.e., "no parking".
Tense and aspect
Past tense: marked by bin (< Eng. been):
Tok Pisin: Na praim minista i bin tok olsem.
English: "And the prime minister spoke thus." (Romaine 1991: 629)
Continuative same tense is expressed through: verb + i stap.
Tok Pisin: Em i slip i stap.
English: "He/She is sleeping." (ibid.: 631)
Completive or perfective aspect expressed through the word pinis (< Eng. finish):
Tok Pisin: Em i lusim bot pinis.
English: "He had got out of the boat." (Mühlhäusler 1984: 462)
Transitive words are expressed through -im (< Eng. him):
Tok Pisin: Yu pinisim stori nau.
English: "Finish your story now!" (ibid.: 640)
Future is expressed through the word "bai" (< Eng. by and by):
Tok Pisin: Bai ol i go long rum.
English: "They will go to their rooms now." (Mühlhäusler 1991: 642)
Development of Tok Pisin
Tok Pisin is a language that developed out of regional dialects of the languages of the local inhabitants and English, brought into the country when English speakers arrived. There were four phases in the development of Tok Pisin that were laid out by Loreto Todd.
Casual contact between English speakers and local people developed a marginal pidgin.
Pidgin English was used between the local people. The language expanded from the users' mother tongue.
As the interracial contact increased, the vocabulary expanded according to the dominant language.
In areas where English was the official language, a depidginization occurred (Todd, 1990).
Tok Pisin is also known as a "mixed" language. This means that it consists of characteristics of different languages. Tok Pisin obtained most of its vocabulary from the English language (i.e., English is its lexifier). The origin of the syntax is a matter of debate. Hymes (Hymes 1971b: 5) claims that the syntax is from the substratum languages—the languages of the local peoples (Hymes 1971b: 5). Derek Bickerton's analysis of creoles, on the other hand, claims that the syntax of creoles is imposed on the grammarless pidgin by its first native speakers: the children who grow up exposed to only a pidgin rather than a more developed language such as one of the local languages or English. In this analysis, the original syntax of creoles is in some sense the default grammar humans are born with.
Pidgins are less elaborated than non-Pidgin languages. Their typical characteristics found in Tok Pisin are:
A smaller vocabulary which leads to metaphors to supply lexical units:
Tok Pisin: vot; English: "election" (n) and "vote" (v)
Tok Pisin: hevi; English: "heavy" (adj) and "weight" (n)
Less differentiated phonology: [p] and [f] are not distinguished in Tok Pisin (they are in free variation). The sibilants/s/, /z/, /ʃ/, /ʒ/, /tʃ/, and /dʒ/ are also not distinguished.
All of the English words "fish", "peach", "feast", and "peace" would have been realised in Tok Pisin as pis. In fact, the Tok Pisin pis means "fish" (and usually has a sound closer to [ɪ], almost like the English word "piss"). English "piss" was reduplicated to keep it distinct: thus pispis means "urine" or "to urinate".
Likewise, sip in Tok Pisin could have represented English "ship", "jib", "jeep", "sieve", or "chief". In fact, it means "ship".
Many words in the Tok Pisin language are derived from English (with Australian influences), indigenous Melanesian languages, and German (part of the country was under German rule until 1919). Some examples:
as—bottom, cause, beginning (from "ass"/"arse"). "As ples bilong em" = "his birthplace". "As bilong diwai" = "the stump of a tree".
bagarap(im)—broken, to break down (from "bugger up")—(the word is commonly used, with no vulgar undertone, in Tok Pisin and even in Papua New Guinea English).
bagarap olgeta—completely broken
balus—bird or more specifically a pigeon or dove (an Austronesian loan word)—by extension aeroplane
belhat—angry (lit. "belly hot")
belo—bell—as in "belo bilong lotu" = "church bell". By extension lunch or midday break (from the bell rung to summon diners to the table). A fanciful derivation has been suggested from the "bellows" of horns used by businesses to indicate the beginning of the lunch hour, but this seems less likely than the straightforward derivation.
bensin—petrol/gasoline (from German Benzin)
bikpela magani—kangaroo (literally "big wallaby")
bubu—grandparent, any elderly relation—also grandchild. Possibly from Hiri Motu, where it is a familiar form of tubu, as in tubuna or tubugu.
hap—a piece of, as in "hap diwai" = a piece of wood. (from "half").
hapsait—the other side (from "half side")
hap ret—purple (from "half red")
haus—house or building (from German Haus and/or English "house")
hausboi/hausmeri—a male/female domestic servant - hausboi (or haus boi) can also mean "servants quarters"
haus kaikai—restaurant (from "house food")
haus moni—bank (from "house money")
haus sik—hospital (from "house sick")
haus dok sik—animal hospital (from "house dog sick")
haus karai—place of mourning (from "house cry")
sit haus (vulgar)—toilet (from "shit house"), also:
smol haus—toilet/bathroom ("small house")
haus tambaran—traditional Sepik-region house with artifacts of ancestors or for honoring ancestors; tambaran means "ancestor spirit" or "ghost"
hevi—heavy, problem. "Em i gat bigpela hevi" = "he has a big problem".
hukim pis—to catch fish (from "hook")
kaikai—food, eat, to bite (Austronesian loan word); also[a]
kaikai bilong moningtaim—breakfast
kaikai bilong nait—dinner/supper
kakaruk—chicken (probably onomatapoetic, from the crowing of the rooster)
kamap—arrive, become (from "come up")
kisim—get, take (from "get them")
lotu—church, worship from Fijian, but sometimes sios is used for "church"
mangi/manki—small boy, by extension, young man (Probably from the English jocular/affectionate usage "monkey", applied to mischievous children, although a derivation from the German Männchen, meaning "little man", has also been suggested)
manmeri—people (from "man", man, and "meri", woman)
maski—it doesn't matter, don't worry about it (Probably from German macht nichts = "it doesn't matter")
maus gras—moustache (lit: "mouth grass")
meri—woman (from the English name "Mary"). Also means female, e.g., "bulmakau meri" (lit. "bull cow female") = cow.
olgeta—all (from "all together")
olsem wanem—what?, what's going on? (Literally "like what"? Sometimes used as an informal greeting, similar to "what's up?" in English)
pisin—bird (from "pigeon"). The homophony of this word with the name of the language has led to a limited association between the two; Mian speakers, for example, refer to Tok Pisin as "wan weng", literally "bird language".
pasim—close, lock (from "fasten")
pasim maus—shut up, be quiet, i.e. "yu pasim maus" lit: "you close mouth" = "shut up!"
paul—wrong, confused, i.e. "em i paul" = "he is confused" (from English "foul")
susa—sister, though nowadays very commonly supplanted by "sista". Some Tok Pisin speakers use "susa" to indicate a sibling of the opposite gender, while a sibling of the same gender as the speaker is a "brata" or "barata".
susu—milk, breasts, from Malay
tambu—forbidden, from "taboo", but also means "in-laws" (mother-in-law, brother-in-law, etc.) and other relatives whom one is forbidden to speak to, or mention the name of, in some PNG customs.
Yumi olgeta mama karim umi long stap fri na wankain long wei yumi lukim i gutpela na strepela tru. Uumi olgeta igat ting ting bilong wanem samting i rait na rong na mipela olgeta i mas mekim gutpela pasin long ol narapela long tingting bilong brata susa.
Article 1 of the Universal Declaration of Human Rights in English:
All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.
^ abLaurie Bauer, 2007, The Linguistics Student’s Handbook, Edinburgh
^The published court reports of Papua New Guinea refer to Tok Pisin as "Pidgin": see for example Schubert v The State  PNGLR 66.
^See the Glottolog entry for Tok Pisin (itself evidence that the linguistic community considers it a language in its own right, and prefers to name it Tok Pisin), as well as numerous references therein.
^Mundhenk, Norm (1990). "Linguistic Decisions in the Tok Pisin Bible". Melanesian Pidgin and Tok Pisin: Proceedings of the First International Conference on Pidgins and Creoles in Melanesia: 372.
^Liklik can also be used as an adverb meaning "slightly", as in dispela bikpela liklik ston, "this slightly big stone".