Kuyʔūn permitted several methods of changing the part of speech of individual lexemes by zero-derivation. The most important processes were as follows:
- ADJ > N
- Adjectives could be turned into abstract inanimate nouns denoting the quality in question by simply inflecting them as a nominal. Definiteness prefixes used with such nouns indicated that a certain degree of the quality was referenced; precisely which degree was meant had to be deduced from context.
- ADJ > ADV
- Adjectives could be turned into adverbs by first nominalising them, and then inflecting them for the instrumental case.
- ADJ > V
- Adjectives could be turned into intransitive, mostly stative verbs by simply applying verbal inflection. Sometimes the addition of a classifier could turn such deadjectival verbs into transitives; however, the more common way of transitivising was inflection for causative voice.
- V > N
- Verbal participles could be inflected nominally to indicate an animate subject noun, usually referring to the agent. As a means to morphologically disambiguate these from the similarly formed verbal action nouns, possessive affixes were usually not added to the pure participle, but to a derived singulative stem using suffixed -co (see -s below).
- N > V
- Nouns could be turned into verbs denoting the process they were the result of by simply inflecting the nominal stem as a verb in the causative voice. A rare but attested further development was voice-stacking, whereby such an inherently causative verb could be inflected for any of the verbal voices, including another layer of causativity. (Strictly speaking, however, this is not "zero-derivation" anymore, but the inflectional causative affix reinterpreted as derivational.)
Due to the rather mangling sound change history of Kuyʔūn, which included several phonemic mergers and widespread syncope of unstressed medial and final vowels, some of the derivational morphology inherited from Adāta had become unproductive. However, new affixes were created from a number of originally separate lexemes, and in addition some methods of derivation were borrowed from Habeo languages.
A common morphophonological change in older derivational affixes was vowel lengthening; this entailed the irregular relationships /ɛ/ > ī and /i/ > ay (which then contracted to ē in closed syllables).
The following derivational affixes were of Adāta vintage:
- A locative suffix that could be added to any part of speech, causing lengthening in preceding stressed vowels, and the (re-)insertion of vowels after stem-final consonants. Not very productive, but found in the lexicon in fossilised lexemes such as cīya "storage room" or kāya "school" as well as in more recent coinages, e.g. šímaya "hometown" from šim- "to live".
- Another suffix that could be added to any part of speech, forming inanimate abstract nouns, often with an inherent collective or plural sense in relation to the unsuffixed lexeme. Immediately preceding stressed vowels always became long before this suffix; and in older formations, consonant deletion was sometimes also observed, often accompanied by the suffix appearing in the allomorph -ʔa, as in the opaque derivation īʔa "family" from len "son". In the productive variant, however, only the usual glottalisation of plosives immediately preceding /l/ did occur. Examples: toyla "prayer" from toya- "to plead", nōcola "court, jury" from nōs "judge".
- A singulative nominaliser, indicating membership in a group or partaking of a characteristic. Could be used with nouns and adjectives, but not with verbs. After consonants the allomorph -so was found (-co after /m n/, -šo after /ʃ/). Examples: čaʔas "member of the city council" from čaʔa "council", leššo "healthy person" from leš "healthy".
- A suffix indicating an associated person (male by default); could be attached to any part of speech. Most occurrences in the lexicon were fossilised, e.g. mayʔo "shepherd" from Ad. māia-rō "pasture-man".
- A suffix attaching to gender-neutral or masculine animate nouns to create a specifically feminine equivalent. Preceding short unstressed /ɑ o/ were deleted, and preceding short unstressed /i ɛ/ were reduced to y where phonotactically possible, coalescing with adjacent /t k ʔ s/ into c č š š. The suffix-final sibilant /ʃ/ itself would fortify into č when possessive affixes were added. Examples: ciskaš "queen" from ciska "king", appaš "girlfriend" from appo "friend".
- An all-purpose adjectivalising suffix; could be added to any part of speech, with lengthening of immediately preceding stressed vowels. After consonants, the variant -in was used, which was of a different, more recent etymological origin (from Adāta ēn "manner, method"). Highly productive. Examples: mołon "watchful" from moło "guard", iʔāwin "descriptive" from iʔāwa- "to describe", somman "optimistic" from somma- "to wish".
- Another adjectivalising suffix, indicating privation (lack of something). After consonants other than /j w/, this suffix was preceded by an epenthetic vowel, usually o. Highly productive, mostly with nominal roots (e.g. mínammi "orphaned" from min "mother", kīsommi "poor" from kīs "gold"), but could also be used with adjectives and adverbs to form antonyms (e.g. péʔammi "cowardly" from peʔa "brave").
- A verbalising suffix, which denoted the typical activity of the noun it attached to. Stem-final /w/ which became /s/ in the 3rd person animate possessed forms did so before this affix as well. A few older formations additionally exhibited dropping of stem-final vowels. Examples: cískata- "to reign" from ciska "king", ōnta- "to cure" from auno "doctor".
Some more recent morphology, innovated from morphemes that were not derivational at the time of Adāta or borrowed from Habeo languages:
- An affectionate diminutive, formed from abesa "neat". This suffix attached only to nouns. Preceding short unstressed /ɑ o/ were deleted, and preceding short unstressed /i ɛ/ were reduced to y where phonotactically possible, coalescing with adjacent /t k ʔ s/ into c č š š. Examples: melos "daddy" from meu "father", pimos "darling" from pimo "star".
- The reverse of -os: a rather formal augmentative/honorific suffix, which could be added to nouns, adjectives, and adverbs, creating nouns that were usually animate. It was derived from pē "big, powerful". Preceding unstressed vowels were deleted after intervocalic /s ʃ m n l j w/, and the resulting clusters were simplified, with the changes /n/ > m, /h/ > s, and /l/ > s or w taking place. Examples: nōspi "supreme judge" from nōs "judge", tyōpi "unity" from tīwa "together".
- This suffix, which was formed from eiabu "instrument, means", derived inanimate instrument nouns from verbs, attaching to the secondary stem with replacement of unstressed stem-final vowels. After stressed stem-final vowels the suffix reduced to -yo with compensatory lengthening, and after single consonants other than /j w ʃ ʧ/, both the stem-final and prefix-initial vowels were dropped. Examples: áymeyo "needle" from ayma- "to sew", éłoʔyo "hearth, oven" from éłoʔa- "to cook", náppeyo "dung, mulch" from nappa- "to grow".
- A suffix resulting from lexicalisation of the Adāta habitual passive singular. It attached to verbs to form an associated patient noun, which could be both animate or inanimate, depending on the referent. In productive usage, the primary stem was used, with any stem-final vowels or diphthongs being replaced by the suffix; if these vowels would have been stressed, the suffix became a long -ō. In the possessed forms, the stem vowel resurfaced, and the suffix allomorphed into -l. Irregular older formations were fairly common, especially with stress-shifting verbs where the difference between primary and secondary stem was significant. Examples: eso "firewood" from eseu, eła- "to burn", čiwo "bridled horse" from čō, čōla- "to tie", teʔmo "commodity" from tekim, teʔma- "to trade", ponno "refugee" from ponna- "to flee".
- A verbal prefix indicating distortion or failure of the action, originating in lexicalisation of the Adāta futilitive mood prefix īra-. Before stem-initial vowels or voiced consonants, the prefix-final /ɑ/ was dropped. Examples: ayʔlało- "to mishear" from lało- "to listen", ayʔnīʔana- "to get lost" from nīʔana- "to turn".
- An iterative verbal prefix, denoting repeated or restarted actions, formed from bō "again". The prefix coalesced with stressed stem-initial short vowels /i ɛ ɑ o/ to poy- poy- pā- pau- in open syllables and to pē- pē- pā- pō- in closed syllables. With unstressed short vowels the same vowel changes occurred (albeit with positional shortening), but the prefix-initial consonant remained /w/. Before long vowels, the prefix became waw-. In some older formations (but not in productive usage), unstressed stem-initial syllables were syncopated. Examples: wosāte- "to restart" from sāte- "to start", woʔlāla- "to pass on" from pilāla- "to send", pāwi- "to say again" from awi- "to say".
- An intensifying verbal prefix, formed from asada "greatly". Before vowels, plosives, and sibilants, the prefix-final /ɑ/ was dropped, with assimilation of stem-initial /s ʦ/ to š č. Examples: ešenta- "to be overwhelmed" from yanta- "to feel", ešalošša- "to testify" from lošša- "to answer".
- A prefix that could attach to adjectives and adverbs, signifying the opposite quality or manner. Cognate to the verbal negative marker ma-, from which it was most likely created by analogy, seeing as it indeed exhibited the exact same allomorphy as the verbal prefix, most importantly dropping of the /ɑ/ before stem-initial vowels. However, it was still clearly derivational rather than an inflectional polarity marker, both because the meaning was at times somewhat idiomatic, and because ordinary negative predication used a negated copula, not a negated adjective. Examples: mátonna "easy" from átonna "difficult", macayō "exceptional" from cayō "frequent, common", mayōʔo "dispensable" from yōʔo "venerable, traditional".
- An attenuative prefix that could attach to adjectives (and, occasionally, to nouns) without changing word class, derived from Y.H. opi "nearly, almost". Before stem-initial /i/ and /p/ the prefix-final /i/ was dropped; before other stem-initial vowels it reduced to y. If this prefix was attached to noun stems, the accent shifted to the first syllable of the prefix. Examples: oppoših "chilly" from poših "cold", ópičisto "minor problem" from čisto "challenge".