Chapter 86The Reciprocal u-

86.1 The prefix u- and its arity effect

The prefix u- ‘reciprocal’ is a valency-decreasing derivational morpheme with arity −1: it fills the object slot of a transitive verb with a mutual or collective participant, detransitivizing the verb Nakagawa (2024: 187–188); Bugaeva & Kobayashi (2022: §4.2.1). The derived verb always takes a plural or collective subject — only two or more participants can stand in a mutual relation. The person-marking diagnostic (the operative test of derived transitivity set out in Chapter 73 (Valency, Voice, and Noun Incorporation: Overview)) confirms the intransitivization: a verb that takes the prefixal A-indexes a= or ci= shifts to the suffixal S-indexes =an or =as after u- Bugaeva & Kobayashi (2022: §4.2.1); Satō (2008: 232–233).

The slot u- occupies is the same nominal/applicative position as the reflexive prefix yay- ‘REFL’, si- ‘AUTOC/ANTIC/REFL; REFL.POSS’, and the antipassive i- ‘antipassive’; these prefixes all decrease or rearrange valency, but their semantic domains differ — self-directed action, autocausative/anticausative/reflexive or reflexive-possessive marking, object defocusing, and mutual participation, respectively. The prefix is highly productive: it attaches to base transitive verbs, to applicative-prefixed stems, and to causativized forms, with the arity calculus predicting the transitivity of each output (see Chapter 73 (Valency, Voice, and Noun Incorporation: Overview)). A further complication is that u- covers not only canonical bilateral reciprocal meaning ('each other') but also joint or associative participation ('together'), and the two readings are not always distinguishable without context.

86.2 The canonical reciprocal

In its canonical use, u- expresses mutual action: each participant in the plural subject simultaneously acts on and is acted on by the others. The paradigm pair koyki ‘fight, attack sb’ (transitive) → u-koyki ‘fight each other’ (intransitive), and siru ‘rub sth’ → u-siru ‘rub each other’, illustrates the productive base pattern Nakagawa (2024: 187–188).

u- also operates on ditransitive (three-argument) bases. When the Addressee or Recipient of a ditransitive is the argument filled by the mutual relation, the construction is termed indirect reciprocal Bugaeva & Kobayashi (2022: §4.2.1). The epenthetic glide w surfaces between u- and a following vowel-initial prefix:

The learner grammar of Ijäs (2023) (Lesson 9-10) also lists unukar ‘meet each other’ (from nukar ‘see sb’) as a standard reciprocal, and gives the pair u-hekote ‘be a married couple (singular)’ / u-hekotpa ‘be a married couple (plural suppletive)’; both are confirmed by the primary sources ‹consensus› Nakagawa (2024: 187–188).

86.3 Joint-participation and collective readings

Several forms with u- do not yield a strictly bilateral 'each other' reading. Here u- signals joint involvement or a two-party social relation without requiring symmetric action between every pair of participants Nakagawa (2024: 187–188).

The clearest instance is u-tures-kor ‘be siblings’, which incorporates the noun tures ‘sibling of the same sex’ and the verb kor ‘have’. The surface subject may be syntactically singular — a young man described in terms of having a sister — yet the verb carries u- because the sibling relation inherently involves two parties:

Similarly, u-mina-re ‘laugh together’ does not mean 'make each other laugh' but 'all laugh together' — a sociative reading arising from the arity calculus: u- (−1) prefixed to the already-causativized intransitive mina-re (arity 2) yields net arity 1 (intransitive), encoding collective action rather than imposing a new causer slot Nakagawa (2024: 188). This u- + causative-on-intransitive path to a sociative reading is treated further in Chapter 86 (The Reciprocal u-) below.

86.4 Semantic types

Bugaeva and Kobayashi identify five constructional types for u- reciprocals, organized by the nature of the mutual relation and the morphosyntactic base Bugaeva & Kobayashi (2022: §4.2.1):

The quasi-possessive type distributes each participant's possessed noun across the group: u-tek-kisma 'shake hands' (lit. 'shake each other's hand') and u-oruspe-nu are further instances Bugaeva & Kobayashi (2022: §4.2.1). For the parallel reflexive construction in which a possessed noun is incorporated with yay- or si-, see Chapter 85 (The Reflexive-Possessive si- and the yay-/si- Division).

86.5 Quasi-possessive reciprocals: formation and motivation

The term quasi-possessive reciprocal describes a reciprocal relation located inside an incorporated nominal. Its structure is [u-N_possessed]-V: u- supplies the possessor of the noun, and the resulting u-N unit is incorporated into the verb. The participants therefore act upon one another through a relationally possessed entity such as words, stories, strength, or hands Alpatov, Bugaeva & Nedjalkov (2007: 1773); Bugaeva & Kobayashi (2022: §4.2.1).

This constituency explains the arity effect. The incorporated noun fills the Theme position of the transitive verb, while u- identifies the noun’s possessor reciprocally with the plural or collective subject. The whole complex has one syntactic argument and behaves as an intransitive predicate. The bracketing for u-itak-nu is therefore [[u-itak]-nu]: first ‘one another’s words’, then ‘hear those words’. This analysis gives each morpheme one role and directly derives the attested intransitive behavior.

86.6 Bare incorporated nouns and word-internal possessors

Possession elsewhere in Ainu commonly uses a person prefix together with an affiliative form of the noun. For example, the concept form tek ‘hand’ has the affiliative forms tek-e and tek-e-he, as in ku=tekehe ‘my hand’ Nakagawa (2024: 217–231). Noun incorporation uses the bare concept stem: u-tek-kisma contains tek. Its possessor is still recoverable because u- stands immediately before the noun inside the verbal word. See Chapter 44 (Concept Form vs. Affiliative (Possessed) Form) for the free nominal paradigm and Chapter 88 (Object (Patient) Noun Incorporation) for the general incorporation pattern.

This is especially transparent with nouns whose interpretation invites a possessor. A hand, a person’s words, and a person’s inner state naturally raise the question ‘whose?’. The word-internal prefixes answer it: u- distributes possessors across participants, yay- links the possessor to an intentional subject, and possessive si- links it to the subject in the lexical patterns that select si-. The bare noun remains inside the predicate, so no separate possessed noun phrase is required.

The reflexive examples show the same architectural principle. In yay-par-oyki and si-etu-uyna, the prefix possesses an incorporated body-part noun Bugaeva & Kobayashi (2022: §4.2.2). Dal Corso identifies the same construction in Sakhalin yay-cise-koro ‘have one’s own house’ and reports cise ‘house’, kotan ‘village’, cara ‘mouth’, and ram ‘soul’ as recurrent incorporated nouns in Piłsudski’s corpus Dal Corso (2024: 73–74). In si-hum-nu-yar, si-hum is ‘one’s own sound’, nu is ‘hear’, and -yar introduces an indefinite hearer Nakagawa (2024: 432). The larger si-ram family lexicalizes mental activity through movements of one’s own ram ‘heart/mind’; its applicative stacks are analyzed in Chapter 85 (The Reflexive-Possessive si- and the yay-/si- Division) and Chapter 82 (Applicative Stacking, Ordering, and the Feeding of Relativization).

86.7 From hearing words to agreement and obedience

The lexical development of u-itak-nu begins with an ordinary social event: participants hear and accept words belonging to one another. Mutual uptake supports the reading ‘agree’, while successful uptake of another person’s direction supports ‘obey’. Tamura defines uitaknu as ‘listen to what each other says; agree/obey’ and explicitly segments it as u-itak-nu Tamura (1996: 808). Bugaeva’s Sakhalin example above independently confirms the obedience reading Bugaeva (2016: 103).

Mandarin tīnghuà is defined as ‘comply’ Ministry of Education (2021). Turkish dictionaries give söz dinlemek as an equivalent of ‘obey’ Cambridge Dictionary (2022), and Dehkhoda groups Persian حرف‌شنوی with obedience and submission Dehkhoda (1931–1973). A corpus study of Biblical Hebrew finds that the valency pattern שמע בקול regularly triggers ‘obey’ Leal & Glanz (2021: 209–211). These parallels establish a recurrent semantic mapping HEAR WORDS/VOICE → HEED → OBEY. They explain the motivation of the Ainu social meaning and carry no claim of common origin or borrowing.

86.8 Aeuitaknup: a nominalized quasi-possessive reciprocal

The title of Batchelor’s 1897 New Testament contains Aeuitaknup ‘covenant, promise, testament’ Batchelor (1897: title page). Batchelor’s 1903 standalone grammar documents the contemporary descriptive framework Batchelor (1903); his 1905 dictionary supplies the lexical definition ‘a covenant; a promise’ and Japanese 誓約、ケイヤク Batchelor (1905: Aeuitaknup). Tajima gives the full morphological analysis a=e-u-itak-nu-p and translates its nominal core as ‘that one another’s words are heard’ Tajima (1992: 66).

The internal derivation proceeds in three layers. First, u-itak denotes ‘one another’s words’. Second, [[u-itak]-nu] denotes mutual hearing or acceptance and has the lexical reading ‘agree/obey’. Third, the applicative e-, fourth-person A marker a=, and nominalizer -p form the title noun. Tajima’s 1992 terminology calls a- passive; this grammar uses the fourth-person analysis developed in later Ainu descriptions. The quasi-possessive constituency of u-itak-nu remains the same under either account.

86.9 The causativized reciprocal

When the productive causative suffix -re is added to an already-reciprocalized intransitive, arity rises by one, and the construction means 'cause sb to do X to each other'. The chain is: base transitive (arity 2) → add u- (−1) → intransitive (1) → add -re (+1) → transitive (2), with a new causer as subject:

The contrasting sociative reading — 'all do X together' — arises when u- is prefixed to a form already causativized from an intransitive base, so that the net arity is 1 − 1 = 0: u-horip-pa-re ‘all dance/exorcise together’, u-kira-re ‘all escape together’ Bugaeva & Kobayashi (2022: §4.3.2). The arity of the base verb and the order of operations determine which reading obtains; surface form alone is insufficient Nakagawa (2024: 188) ‹corpus-suggested›.

86.10 Lexicalized forms and extension to non-verbal bases

A range of forms with u- have undergone semantic specialization to the point where the mutual motivation is conventional. Kin- and social-relation verbs such as u-tures-kor ‘be siblings’ and u-hekote ‘be a married couple’ encode relational membership. unukar ‘meet each other’ is the standard word for 'meet' in Saru Nakagawa (2024: 187–188).

The prefix extends beyond the verb paradigm to locative nouns, postpositions, and adverbs: u-sam ‘near each other’, u-tura ‘together’, u-neno ‘similar to each other’ Bugaeva & Kobayashi (2022: §4.2.1).

Two further forms show opacity. uwanpare ‘gaze intently’ decomposes as u-anpa-re (RECP-carry-CAUS), but the semantic path from 'cause each other to carry' to 'observe intently' is unresolved in the sources ‹contested› aynu-corpora Discord (2023–2026) (nukopoli, aynu-corpora Discord, 2024). uwatte ‘multiply, breed (of animals)’ has been analysed as u-w-at-te (RECP-EP-attach-CAUS); the semantic path 'cause each other to cling/pair' → 'breed' is plausible for a verb restricted to animal populations, and its complement uwaste ‘increase (of humans, plants)’ is semantically differentiated aynu-corpora Discord (2023–2026) (gengojiro, aynu-corpora Discord, 2024) ‹corpus-suggested›.

86.11 The sociative uko- and uwe-

The prefixes uko- ‘together, mutually’ and uwe- ‘together, mutually’ are synchronically unitary markers but decompose as u- + ko- and u- + e- respectively Nakagawa (2024: 208, 211–212); Bugaeva & Kobayashi (2022: §4.3.2). Because the applicative contributes arity +1 and u- contributes −1, the net arity change is zero: the sociative is valency-neutral. The transitive verb kor ‘have’ starts with arity 2. Plain u-kor ‘marry (lit. have each other)’ applies only reciprocal u-, so 2 − 1 = 1 and the result is intransitive. In u-ko-kor ‘have together’, sociative uko- combines ko- (+1) with u- (−1), for a net change of 0; 2 + 0 = 2, and the result remains transitive Nakagawa (2024: 208):

uko- is commoner than uwe- in Saru texts, reflecting the higher productivity of ko- as an applicative Bugaeva (2006: 188). The two are partially interchangeable in derivationally transparent forms (uko-yaykopuntek ~ uwe-yaykopuntek 'rejoice together'), but ko-'s comitative and goal-directed semantics give it the advantage where joint orientation toward shared participants is foregrounded Bugaeva & Kobayashi (2022: §4.3.2). For the full applicative semantics of ko- and e-, see Chapter 78 (The Applicative System: Overview and the Preverb-vs-Applicative Debate); for their stacking with other prefixes, Chapter 82 (Applicative Stacking, Ordering, and the Feeding of Relativization).