Echo vowels

Tapayúna has a phenomenon whereby an echo vowel is inserted in words whose underlying form ends in a consonant.^[7]: 100 The epenthesized vowels are unstressed, as in rowo [ˈɾɔwɔ] ‘jaguar’, tàgà [ˈtʌgʌ] ‘bird’, khôgô [ˈkʰogo] ‘wind’.

Finiteness

As in all other Northern Jê languages, verbs inflect for finiteness and thus have a basic opposition between a finite form (also Short Form and main form^[2]: 123) and a nonfinite form (also Long Form^[2]: 123). Finite forms are used in matrix clauses only, whereas nonfinite forms are used in all types of subordinate clauses as well as in some matrix clauses (including negated, future, and progressive clauses^[2]: 123). Nonfinite forms are most often formed via suffixation and/or prefix substitution. Some verbs (including all descriptives with the exception of katho ‘to leave’, whose nonfinite form is kathoro) lack an overt finiteness distinction.

The available nonfinite suffixes are /-ɾ/ (the most common option, found in many transitive and intransitive verbs), /-j/ (found in transitive verbs and in some intransitives whose stem ends in the vowel /a/), as well as /-k/ and /-p/ (found in a handful of intransitive verbs which take a nominative subject when finite), as shown in the table below.^{[2][3]: Appendix D}

In Proto-Northern Jê, several verbs derived their finite forms by means of leniting the stem-final consonant (*-t, *-c, *-k → *-r, *-j, *-r).^[6]: 544 In Tapayúna, at least two verbs retain this pattern, though the relation between the finite and nonfinite forms has been obfuscated by a series of regular sound changes, including *-ôj > -wâj (-âj after a labial), *-c > -t.^[2]

The erstwhile palatalizing prefix

In Proto-Northern Jê, a small set of verbs formed their nonfinite forms by employing one of the aforementioned processes and a morphophonological process whereby the onset of the stressed syllable became palatal, and the nucleus of the stressed syllable was raised (if possible); this has been attributed to the influence of an underlying palatalizing nonfinite prefix. In Tapayúna, at least two verbs still follow the archaic pattern.^[6]

Prefix substitution or loss

In addition to the aforementioned processes, the finiteness inflection may involve prefix substitution or loss. For example, the valency-reducing prefixes are a(j)- (anticausative) and a- (antipassive) in finite verb forms, but wi- and tá-/tu-, respectively, in the nonfinite forms.^{[6]: 541, 544} In addition, some verbs which denote physiological activities or movement have a prefix (i- and a-, respectively) in their finite forms but not in the nonfinite form. Some examples are given below.^{[3]: Appendix D}

Nominal number

Nouns which denote human beings may receive the plural suffix -jê,^{[2]: 70, 87} as in wẽwyjê ‘men’ (← wẽwy) ‘man’.

Productive affixes

Tapayúna makes use of the diminutive suffixes -tĩ and -re, as well as of the augmentative suffix -txi.^{[2]: 69, 79–81} Examples include: taratĩ ‘its small wing’ or taratĩre ‘its tiny wing’ (← tara ‘its wing’, an inflected form of jara ‘wing’), hrytĩ ‘small, narrow path’ or hrytĩre ‘a very narrow path’ (← hry ‘path’), thêtxi ‘tick’ (← thê), wĩtxi ‘alligator’ (← wĩ).

Nominalizations which denote instruments and places are formed by means of attaching the suffix -tà to the nonfinite form of a verb: kahõ ‘to sweep’ → kahõj ‘to sweep (nonfinite)’ → kahõjtà ‘broom’; wẽ ‘people’ + khrĩ ‘to sit (plural, finite = nonfinite)’ → wẽkhrĩtà ‘seat’.^[2]: 81

Agent nominalizations are formed by means of attaching the suffix -kanê to the nonfinite form of a verb: hwitô ‘leaf; paper’ + tôk ‘to paint; to write’ → hwĩtôtôkkanê ‘teacher’.^[2]: 82