Chapter 136Causal and Purpose Clauses (kusu)

136.1 Overview: kusu in the causal–purposive group

Among Hokkaido Ainu's conjunctive particles, kusu stands out as the only member whose primary meaning spans two semantic relations: it marks the preceding clause as either the reason or cause of the following event, or the purpose or aim toward which the following clause's action is directed. Nakagawa assigns it, together with wa kusu and hi kusu, to group ⑥ (原因・目的, 'cause/purpose') of his seven-way semantic taxonomy of conjunctive particles Nakagawa (2024: 352–353). Refsing places the same particle under her "Consequential" grouping alongside kunine and na for Shizunai Refsing (1986: 238, 251–253). Satō treats it in the section adjacent to korka 'but', contrasting purposive and causal readings Satō (2008: 53–54). The three sources agree on the central fact: the single particle kusu covers both cause and purpose, and the reading is determined by context.

Two reason-only compound particles restrict the semantic range. Wa kusu foregrounds a completed event as the cause of the main clause; the sequential wa signals that the preceding event actually took place. Hi kusu is the formal-noun construction hi ('the fact/time of') + kusu and similarly carries reason only Nakagawa (2024: 353); Ijäs (2023). The three particles and their properties are given in the table below.

The final vowel of kusu is frequently devoiced in running speech, yielding the variant kus; this is a phonological process, not a distinct lexeme. The segmentally identical material also enters the intentive auxiliary kusu ne 'be going to; intend to' and the indirect-speech complementizer use treated in Chapter 107 (The kuni Complementizer and Purpose Complements). The inventory context for kusu is established in the clause-linkage overview.

136.2 Purpose: 'in order to'

When kusu marks purpose, the preceding clause describes the goal or aim of the action in the following clause, and the following clause is typically a motion verb. This distributional tendency is strong and is explicitly noted by Nakagawa Nakagawa (2024: 353). The purpose-marked clause occupies the adverbial slot of a prospective complement: the event it describes has not yet occurred at the time of the motion.

The purposive reading is available whenever the following clause describes a transition, displacement, or initiation rather than a completed past event. For purpose complements governed by a transitive verb of thinking, saying, or wanting, the complementizer kuni ‘(purpose/irrealis complementizer)’ takes over the embedding role; the boundary between adverbial kusu and complementizing kuni is treated in Chapter 107 (The kuni Complementizer and Purpose Complements). A rarer purpose-adverbial, kunine (kuni + copula ne), is attested in Satō and Refsing but is less productive than plain kusu in this function Satō (2008: 53); Refsing (1986: 252).

136.3 Reason and cause: 'because'

The reason/cause reading of kusu treats the preceding clause as the motivation, antecedent condition, or cause of the following one. The preceding clause typically describes a state of affairs that holds or held at the time the speaker asserts the consequent. The following example shows kusu after a desiderative clause: the speaker's desire to pursue is the stated reason for preparing the boat.

When the cause is a realized state of affairs, the same kusu applies. In the following example a formal-noun predicate (p ne) closes the cause clause before kusu introduces the consequence.

Refsing documents the same structure in Shizunai: kusu introducing a consequence after a stative cause clause ('yesterday since the weather was fine, the three of us strolled over the mountain') Refsing (1986: 251). The cause-clause predicate type (desiderative, formal-noun, stative) does not by itself determine the choice of kusu; the cause reading is the more accessible one wherever the preceding clause describes a completed or persistent state.

136.4 The evidential–kusu scope order

A conjunctive particle attaches outside the clause-final evidential frame. When a cause clause closes on an evidential nominalizer such as ruwe ne or hawe ne, kusu follows the evidential rather than intervening between the verb and it. Nakagawa states the ordering for all linkers: predicate – evidential – connective Nakagawa (2024: 393). The following attested example from Kawakami Matsuko's Saru oral narrative shows the reportative evidential haw-e ne followed directly by kusu.

The ordering constraint has a corollary for the intentive auxiliary. When causal kusu follows a ruwe ne evidential, the string ruwe ne kusu is well formed and frequently attested; however, the intentive kusu ne requires an opposite arrangement — kusu ne ruwe ne — and is not licensed after ruwe ne, making *ruwe ne kusu ne ungrammatical Nakagawa (2024: 393). Nukopoli characterized this as a scope hierarchy in which the intentive modal must scope outside the evidential, and the characterization is corroborated by the published account (aynu-corpora Discord (2023–2026), nukopoli, aynu-corpora Discord 2024). The evidential system and its interaction with clause-linking material is treated in the ruwe ne chapter.

136.5 wa kusu and hi kusu: reason-only compounds

The compound wa kusu restricts the meaning to cause and reason, excluding the purpose reading. The sequential particle wa signals that the preceding event is completed and its result-state is in force; kusu then marks that actualized event as the cause of the main clause Nakagawa (2024: 353); Ijäs (2023). Because the preceding event must be actualized for wa to apply, a future or hypothetical purpose clause — which by definition has not yet occurred — is incompatible with wa kusu. The following constructed example illustrates the compound.

Satō cites an adversative frame in Chitose where wa kusu occurs inside a sentence headed by korka 'but': the speaker wanted to go to town but the addressee's arrival (e=ek wa kusu) caused the cancellation Satō (2008: 53). The construction is well represented in colloquial speech across Hokkaido.

Hi kusu is a distinct compound: the formal noun hi ‘the fact of; place, time’ nominalizes the preceding clause ('the fact that …'), and kusu marks it as cause. The result closely parallels plain kusu in meaning — reason only — but the formal-noun nominalizer adds a more explicit factual presupposition. Nakagawa confirms the reason-only reading and notes that hi kusu is common in Saru and Chitose but rare and dialectally variable outside those varieties Nakagawa (2024: 353).

Refsing identifies a set of lexicalized compounds built on kusu/kus in Shizunai: nekusu 'therefore', wakusu 'so that', and the interrogative nepkus 'why' Refsing (1986: 252). These frozen compounds represent the end-point of lexicalization within the same grammaticalization pathway that gives rise to the free conjunctive use described in the next section.

136.6 The free conjunctive use: 'therefore, that is why'

An ordinary conjunctive particle is bound to the predicate it closes and does not head a sentence. Kusu is exceptional: it can appear sentence-initially as a free connective adverb meaning 'therefore; that is why' (Japanese そのために), straddling the boundary between conjunctive particle and conjunction Nakagawa (2024: 353). This free use is noted in the clause-linkage overview; see the particle/adverb distinction. In this position, kusu links a preceding discourse unit to the following clause as its consequence or result, functioning as a clause-level connective adverb rather than a post-predicate particle.

Refsing's lexicalized Shizunai compound nekusu 'therefore' carries the same discourse function in more grammaticalized form Refsing (1986: 252). In contemporary teaching Ainu and learner speech the partially translated form sorekusu — Japanese それ 'that' plus Ainu kusu — occupies the same slot as a sentence opener meaning 'that is why; therefore' (aynu-corpora Discord (2023–2026), thegodofneet, aynu-corpora Discord 2025) ‹contested›. The classical Hokkaido equivalent is the sentence-initial free kusu documented by Nakagawa, or its Shizunai counterpart nekusu; sorekusu is a revitalization-context form that integrates the Japanese demonstrative as a topic antecedent.

136.7 kusu ne: the intentive and prospective construction

When kusu is followed by the copula ne ‘be’ with no person-marking affix, the combination grammaticalizes toward an auxiliary meaning 'be going to; intend to' — the intentive or prospective Nakagawa (2024: 435); Refsing (1986: 252). The absence of person marking on ne is the diagnostic: ordinary copular predicates carry person indexes, but in kusu ne the copula is a grammaticalized element of the complex, and person is already encoded on the preceding verb. Ijäs teaches the phonologically reduced form kusne alongside the fuller kusu ne, reflecting reduction in everyday speech Ijäs (2023).

The construction's semantics spans intentionality, prospective aspect (an event about to occur), and future-oriented modality. Nakagawa places kusu ne in the 意志・必然 (volition/necessity) section of his auxiliary inventory Nakagawa (2024: 435). Nukopoli (aynu-corpora Discord, 2024) characterizes kusu ne as covering both intentionality and tense, analogous to English will; this is a community-proposed extension of the description that available published sources do not fully adjudicate (aynu-corpora Discord (2023–2026)) ‹speculative›. The modal and deontic extensions — in particular the 'must, should' readings — are treated in Chapter 118 (Deontic Necessity and Obligation (kuni ne, kus ne)), and the construction's place in the broader TAM system in Chapter 108 (Tense, Aspect, Mood, and Modality: Overview).

Refsing additionally reports a Shizunai intentional construction kusu ki, where the generic verb ki ‘do’ replaces the copula Refsing (1986: 252). This is a dialect-specific instantiation of the same purposive-to-intentive grammaticalization path ‹corpus-suggested›.

136.8 The causal–purpose polysemy: how the readings are resolved

Several factors favour the purpose reading of bare kusu: a motion or initiation verb in the main clause, a prospective or unrealized event in the marked clause, and a goal-oriented relationship between the actor of the marked clause and the actor of the main clause. Factors favouring the cause reading include completed or stative predicates in the marked clause, an evidential tail before kusu, and a disjoint event-time relationship between the two clauses.

Satō makes the clearest separation: he treats kusu after a formal-noun predicate as cause, and in proximity to a motion verb as purpose Satō (2008: 53–54). Nakagawa gives both readings under a single entry and notes the motion-verb clustering for purpose Nakagawa (2024: 352–353). Ijäs, following Nakagawa, presents the gloss 'because / so / in order to' as a single continuum and identifies motion-verb clustering as the most reliable purpose-cue in text Ijäs (2023). The polysemy itself is uncontroversial across sources; what the accessible sources do not provide is a formal-syntactic account that would predict the reading from structure alone ‹speculative›.

136.9 Dialect range and Sakhalin contrast

Within Hokkaido, the distribution of the three particles is uneven. Hi kusu is confirmed for Saru and Chitose; Nakagawa flags it as rare and dialectally variable outside those varieties Nakagawa (2024: 353). For Shizunai, Refsing's grammar documents kusu in all the functions described here and adds the lexicalized compounds Refsing (1986: 251–253).

The Sakhalin varieties present a typologically notable divergence. In Sakhalin Ainu, kusu does not mark cause or purpose but instead covers the action-continuation and result-state range that Hokkaido splits between kor (simultaneous action) and wa (result-state after completion) Nakagawa (2024: 344). The Sakhalin particle is therefore a false cognate for Hokkaido purposes: segmentally identical but functionally divergent. This contrast is summarized in Chapter 131 (Clause Linkage in Ainu: Typology and Inventory) and is relevant to Chapter 134 (Simultaneous kor 'while' and Overlapping-Event Clauses).