Third person singular present tense of coact; he, she, or it acts together with others.
From 'coact' + '-s' (third person singular present suffix). This is the regular conjugation of coact when the subject is singular and the action is happening in the present.
English's third-person '-s' suffix (he runs, she walks, it coacts) is one of the last surviving verb conjugations in Modern English, showing how much our language has simplified since Middle English.
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