Coact comes from Latin coāctāre or formed in English from the prefix co- 'together' + act, ultimately from Latin agere 'to do, drive'. The historical trail runs through co- in Latin and agere in Latin. Morphologically, coact is transparent: it draws on Latin coāctāre or formed in English from the prefix co- 'together' + act, ultimately from Latin agere 'to do, drive'. Used as a verb, coact now means "act together or jointly", so the present definition can be read against the older forms and meanings. The same lexical family is also visible in derived forms such as coaction, coactive, and coactor and related forms such as act and coaction. The result is a borrowed or transmitted form whose modern spelling carries a compact record of its route into English.