Fusional languages

Morphemes in fusional languages are not readily distinguishable from the root or among themselves. Several grammatical bits of meaning may be fused into one affix. Morphemes may also be expressed by internal phonological changes in the root (i.e. morphophonology), such as consonant gradation and vowel gradation, or by suprasegmental features such as stress or tone, which are of course inseparable from the root.

Most Indo-European languages are fusional to a varying degree. A remarkably high degree of fusionality is also found in certain Sami languages such as Skolt Sami.

Polysynthetic languages

In 1836, Wilhelm von Humboldt proposed a third category for classifying languages, a category that he labeled polysynthetic. (The term polysynthesis was first used in linguistics by Peter Stephen DuPonceau who borrowed it from chemistry.) These languages have a high morpheme-to-word ratio, a highly regular morphology, and a tendency for verb forms to include morphemes that refer to several arguments besides the subject (polypersonalism). Another feature of polysynthetic languages is commonly expressed as "the ability to form words that are equivalent to whole sentences in other languages". The distinction between synthetic languages and polysynthetic languages is therefore relative: the place of one language largely depends on its relation to other languages displaying similar characteristics on the same scale.

Many Amerindian languages can be considered polysynthetic. Inuktitut is one example, for instance the word-phrase: tavvakiqutiqarpiit roughly translates to "Do you have any tobacco for sale?".