The degree of synthesis refers to the morpheme-to-word ratio. Languages with more than one morpheme per word are synthetic. Polysynthetic languages lie at the extreme end of the synthesis continuum with a very high number of morphemes per word (at the other extreme are isolating or analytic languages with only one morpheme per word). These highly synthetic languages often have very long words that correspond to complete sentences in less synthetic languages.
Many, if not most, languages regarded as polysynthetic include agreement with object arguments as well as subject arguments in verbs. Incorporation (primarily noun incorporation) has been an issue that has historically been confused with polysynthesis and also used as a criterion for its definition. Incorporation refers to the phenomenon where lexical morphemes (or lexemes) are combined together to form a single word. Not all polysynthetic languages are incorporating, and not all incorporating languages are polysynthetic.
A contrast was made by some linguists between oligosynthetic and polysynthetic languages, where the former term was applied to languages with relatively few morphemes. The distinction is not widely used today.
Mark C. Baker has tried to define polysynthesis as a syntactic macroparameter within Noam Chomsky's "principles and parameters" programme. He defines polysynthetic languages as languages that conform to the syntactic rule that he calls the "polysynthesis parameter" and which as a result show a special set of morphological and syntactic properties. The polysynthesis parameter states that all phrasal heads must be marked with either agreement morphemes of their direct argument or else incorporate these arguments in that head. This definition of polysynthesis leaves out some languages that are commonly stated as examples of polysynthetic languages (such as Inuktitut), but can be seen to be the reason of certain common structural properties in others such as Mohawk and Nahuatl. Baker's definition, probably because of its heavy dependence on Chomskian theory, has not been accepted as a general definition of polysynthesis.
The term "polysynthesis" was probably first used in a linguistic sense by Peter Stephen DuPonceau (a.k.a. Pierre Étienne Duponceau) in 1819 as a term to describe American languages:
Three principal results have forcibly struck my mind... They are the following:
- That the American languages in general are rich in grammatical forms, and that in their complicated construction, the greatest order, method and regularity prevail
- That these complicated forms, which I call polysynthesis, appear to exist in all those languages, from Greenland to Cape Horn.
- That these forms appear to differ essentially from those of the ancient and modern languages of the old hemisphere. (Duponceau 1819:xxii-xxiii)
The manner in which words are compounded in that particular mode of speech, the great number and variety of ideas which it has the power of expressing in one single word; particularly by means of the verbs; all these stamp its character for abundance, strength, and comprehensiveness of expression, in such a manner, that those accidents must be considered as included in the general descriptive term polysynthetic. (Duponceau 1819:xxvii)
I have explained elsewhere what I mean by a polysynthetic or syntactic construction of language.... It is that in which the greatest number of ideas are comprised in the least number of words. This is done principally in two ways. 1. By a mode of compounding locutions which is not confined to joining two words together, as in the Greek, or varying the inflection or termination of a radical word as in the most European languages, but by interweaving together the most significant sounds or syllables of each simple word, so as to form a compound that will awaken in the mind at once all the ideas singly expressed by the words from which they are taken. 2. By an analogous combination of various parts of speech, particularly by means of the verb, so that its various forms and inflections will express not only the principal action, but the greatest possible number of the moral ideas and physical objects connected with it, and will combine itself to the greatest extent with those conceptions which are the subject of other parts of speech, and in other languages require to be expressed by separate and distinct words.... Their most remarkable external appearance is that of long polysyllabic words, which being compounded in the manner I have stated, express much at once.(Duponceau 1819:xxx-xxxi)
The terms synthetic and polysynthetic were first used in the modern sense by Edward Sapir in the 1920s.
Examples of polysynthetic languages include Inuktitut, Mohawk, Classical Ainu, Central Siberian Yupik, Cherokee, Sora, Chukchi and numerous other languages of the Americas, Siberia, Caucasus and northern Australia.
From Classical Ainu, another polysynthetic, incorporating, and agglutinating language:
|'I keep swaying my heart afar and toward myself over various rumors.' (i.e., I wonder about various rumors.)|
|(Shibatani 1990: 72)|
An example from Western Greenlandic, a polysynthetic and agglutinating language (Fortescue 1983:97; cited in Evans and Sasse 2002):
Polysynthetic languages have arisen in many places around the world. The list below gives some families that are stereotypically polysynthetic, although some members of the families may be less so than others.
Not all languages can be easily classified as being completely polysynthetic. Morpheme and word boundaries are not always clear cut, and languages may be highly synthetic in one area but less synthetic in other areas (compare verbs and nouns in Southern Athabaskan languages).