A synthetic language is a language that is statistically characterized by a higher morpheme-to-word ratio. Rule-wise, a synthetic language is characterized by denoting syntactic relationship between the words via inflection and agglutination, dividing them into fusional or agglutinating subtypes of word synthesis. Further divisions include polysynthetic languages (most of them belonging to an agglutinative subtype, although Navajo and other Athabaskan languages are often classified as belonging to a fusional subtype) and oligosynthetic languages (only found in constructed languages). In contrast, rule-wise, the analytic languages rely more on auxiliary verbs and word order to denote syntactic relationship between the words.

Adding morphemes to a root word is used in inflection to convey a grammatical property of the word, such as denoting a subject or an object.^[1] Combining two or more morphemes into one word is used in agglutinating languages, instead.^[2] For example, the word fast, if inflectionally combined with er to form the word faster, remains an adjective, while the word teach derivatively combined with er to form the word teacher ceases to be a verb. Some linguists consider relational morphology to be a type of derivational morphology, which may complicate the classification.^[3]

Forms of synthesis

Derivational and relational morphology represent opposite ends of a spectrum; that is, a single word in a given language may exhibit varying degrees of both of them simultaneously. Similarly, some words may have derivational morphology while others have relational morphology.

Derivational synthesis

In derivational synthesis, morphemes of different types (nouns, verbs, affixes, etc.) are joined to create new words. That is, in general, the morphemes being combined are more concrete units of meaning.^[3] The morphemes being synthesized in the following examples either belong to a particular grammatical class – such as adjectives, nouns, or prepositions – or are affixes that usually have a single form and meaning:

• German

• This word demonstrates the hierarchical construction of synthetically derived words:

1. Aufsichtsratsmitglieder "members of [the] supervisory board" + Versammlung "meeting"
   1. Aufsichtsrat "supervisory board" + s (Fugen-s) + Mitglieder "members"
      1. Aufsicht "supervision" + s + Rat "council, board"
         1. auf- "on, up" + Sicht "sight"
      2. Mitglied "member" + -er plural
         1. mit- "co-" + Glied "element, constituent part"
   2. ver- (a verb prefix of variable meaning) + sammeln "to gather" + -ung present participle

• auf-, mit-, -er, ver-, and -ung are all bound morphemes.

• Greek

• Polish

• English

• English word chains such as child labour law may count as well, because it is merely an orthographic convention to write them as isolated words. Grammatically and phonetically they behave like one word (stress on the first syllable, plural morpheme at the end).

• Russian

• Persian

• Ukrainian

• international classical compounds based on Greek and Latin

• alternately, cholesterol can be read as chole- + στερεός(stereós) + -ol, as in "bile + solid + [alcohol suffix]", or "the solid alcohol present in bile".

Relational synthesis

In relational synthesis, root words are joined to bound morphemes to show grammatical function. In other words, it involves the combination of more abstract units of meaning than derivational synthesis.^[3] In the following examples many of the morphemes are related to voice (e.g. passive voice), whether a word is in the subject or object of the sentence, possession, plurality, or other abstract distinctions in a language:

• Italian

• Spanish

• Nahuatl

• Latin

• Albanian
  • jepmani
    • "give + to me + it[singular] + you[plural] + [imperative mood]"
    • 'You, give it to me'
• Japanese

• Finnish

• Hungarian

• Turkish

• Georgian

• • The word describes the whole sentence that incorporates tense, subject, object, relation between them, direction of the action, conditional and causative markers etc.

Types of synthetic languages

Agglutinating languages

Agglutinating languages have a high rate of agglutination in their words and sentences, meaning that the morphological construction of words consists of distinct morphemes that usually carry a single unique meaning.^[4] These morphemes tend to look the same no matter what word they are in, so it is easy to separate a word into its individual morphemes.^[1] Morphemes may be bound (that is, they must be attached to a word to have meaning, like affixes) or free (they can stand alone and still have meaning).

• Swahili is an agglutinating language.^[1] For example, distinct morphemes are used in the conjugation of verbs:
  • Ni-na-soma: I-present-read or I am reading
  • U-na-soma: you-present-read or you are reading
  • A-na-soma: s/he-present-read or s/he is reading

Fusional languages

Fusional languages are similar to agglutinating languages in that they involve the combination of many distinct morphemes. However, morphemes in fusional languages are often assigned several different lexical meanings, and they tend to be fused together so that it is difficult to separate individual morphemes from one another.^[1][5]

Polysynthetic

Polysynthetic languages are considered the most synthetic of the three types because they combine multiple stems as well as other morphemes into a single continuous word. These languages often turn nouns into verbs.^[1] Many Native Alaskan and other Native American languages are polysynthetic.

• Mohawk: Washakotya'tawitsherahetkvhta'se means "He ruined her dress" (strictly, 'He made the-thing-that-one-puts-on-one's body ugly for her'). This one inflected verb in a polysynthetic language expresses an idea that can only be conveyed using multiple words in a more analytic language such as English.

Oligosynthetic

Oligosynthetic languages are a theoretical notion created by Benjamin Whorf. Such languages would be functionally synthetic, but make use of a very limited array of morphemes (perhaps just a few hundred). The concept of an oligosynthetic language type was proposed by Whorf to describe the Native American language Nahuatl, although he did not further pursue this idea.^[6] Though no natural language uses this process, it has found its use in the world of constructed languages, in auxlangs such as aUI.

Synthetic and analytic languages

Synthetic languages combine (synthesize) multiple concepts into each word. Analytic languages break up (analyze) concepts into separate words. These classifications comprise two ends of a spectrum along which different languages can be classified. The present-day English is seen as analytic, but it used to be fusional. Certain synthetic qualities (as in the inflection of verbs to show tense) were retained.

The distinction is, therefore, a matter of degree. The most analytic languages, isolating languages, consistently have one morpheme per word, while at the other extreme, in polysynthetic languages such as some Native American languages^[7] a single inflected verb may contain as much information as an entire English sentence.

In order to demonstrate the nature of the isolating-analytic–synthetic–polysynthetic classification as a "continuum", some examples are shown below.

Isolating

• Mandarin lacks inflectional morphology almost entirely, and most words consist of either one- or two-syllable morphemes, especially due to the very numerous compound words.

However, with rare exceptions, each syllable in Mandarin (corresponding to a single written character) represents a morpheme with an identifiable meaning, even if many of such morphemes are bound. This gives rise to the common misconception that Chinese consists exclusively of "words of one syllable". As the sentence above illustrates, however, even simple Chinese words such as míngtiān 'tomorrow' (míng "next" + tīan "day") and péngyou 'friend' (a compound of péng and yǒu, both of which mean 'friend') are synthetic compound words.

The Chinese language of the classic works (of Confucius for example) and southern dialects to a certain extent is more strictly monosyllabic: each character represents one word. The evolution of modern Mandarin Chinese was accompanied by a reduction in the total number of phonemes. Words which previously were phonetically distinct became homophones. Many disyllabic words in modern Mandarin are the result of joining two related words (such as péngyou, literally "friend-friend") in order to resolve the phonetic ambiguity. A similar process is observed in some English dialects. For instance, in the Southern dialects of American English, it is not unusual for the short vowel sounds [ɪ] and [ɛ] to be indistinguishable before nasal consonants: thus the words "pen" and "pin" are homophones (see pin-pen merger). In these dialects, the ambiguity is often resolved by using the compounds "ink-pen" and "stick-pin", in order to clarify which "p*n" is being discussed.

Analytic

• English:
  • "He travelled by hovercraft on the sea" is largely isolating, but travelled (although it is possible to say "did travel" instead) and hovercraft each have two morphemes per word, the former being an example of relational synthesis (inflection), and the latter of compounding synthesis (a special case of derivation with another free morpheme instead of a bound one).

Rather synthetic

• Japanese:
  • 私たちにとって、この泣く子供の写真は見せられがたいものです。 Watashitachi ni totte, kono naku kodomo no shashin wa miseraregatai mono desu means strictly literally, "To us, these photos of a child crying are things that are difficult to be shown", meaning 'We cannot bear being shown these photos of a child crying' in more idiomatic English. In the example, most words have more than one morpheme and some have up to five.
• Hebrew:
  • אתמול סיפרתי לחברים שלי על הרעיון, שעליו חשבתי‎ Etmol siparti l'khaverim sheli al hara'ayon, she'alav khashavti. this sentence means "Yesterday I told my friends about the idea I was thinking about". From this example we can see that Hebrew verbs are conjugated by tense/mood and person (including gender and number). In addition, there are prepositions that are also conjugated, but by person, like של‎ shel and על‎ al. More at: Modern Hebrew grammar.

Very synthetic

• Finnish:
  • Käyttäytyessään tottelemattomasti oppilas saa jälki-istuntoa
  • "Should they behave in an insubordinate manner, the student will get detention."
  • Structurally: behaviour (present/future tense) (of their) obey (without) (in the manner/style) studying (they who (should be)) gets detention (some). Practically every word is derived and/or inflected. However, this is quite formal language, and (especially in speech) would have various words replaced by more analytic structures: Kun oppilas käyttäytyy tottelemattomasti, hän saa jälki-istuntoa meaning 'When the student behaves in an insubordinate manner, they will get detention'.
• Georgian:
  • გადმოგვახტუნებინებდნენო gadmogvakht'unebinebdneno (gad-mo-gv-a-kht'un-eb-in-eb-d-nen-o)
  • 'They said that they would be forced by them (the others) to make someone to jump over in this direction'.
  • The word describes the whole sentence that incorporates tense, subject, direct and indirect objects, their plurality, relation between them, direction of the action, conditional and causative markers, etc.
• Classical Arabic:
  • أوأعطيناكموه عبثًا؟ ’awa’aʼṭaynākumūhu ʻabathan (wa-aʻṭay-nā-ku-mū-hu ʻabath-an)
  • "And did we give it (masc.) to you futilely?" in Arabic, each word consists of one root that has a basic meaning (aʻṭā  'give' and ʻabath  'futile'). Prefixes and suffixes are added to make the word incorporate subject, direct and indirect objects, number, gender, definiteness, etc.

Increase in analyticity

Haspelmath and Michaelis^[8] observed that analyticity is increasing in a number of European languages. In the German example, the first phrase makes use of inflection, but the second phrase uses a preposition. The development of preposition suggests the moving from synthetic to analytic.

It has been argued that analytic grammatical structures are easier for adults learning a foreign language. Consequently, a larger proportion of non-native speakers learning a language over the course of its historical development may lead to a simpler morphology, as the preferences of adult learners get passed on to second generation native speakers. This is especially noticeable in the grammar of creole languages. A 2010 paper in PLOS ONE suggests that evidence for this hypothesis can be seen in correlations between morphological complexity and factors such as the number of speakers of a language, geographic spread, and the degree of inter-linguistic contact.^[9]

According to Ghil'ad Zuckermann, Modern Hebrew (which he calls "Israeli") "is much more analytic, both with nouns and verbs", compared with Classical Hebrew (which he calls "Hebrew").^[10]