What is the Latin word for complement?

The usual Latin words for “complement” are complēmentum, refectiō, supplēmentum. The right choice depends on the sense; see the distinctions below.

English → Latin

“complement” in Latin

complēmentumcomplement (that which fills up or completes); completion refectiōremaking; restoration, repair; refreshment, recreation supplēmentumreinforcements; supplies

The English word complement itself goes back to Latin pleō, through complēmentum.

Riddle & Arnold A Copious and Critical English–Latin Lexicon, 1864

complement

complementum: refectio (making whole again or repairing): supplementum (that which makes anything whole; e.g., supplementum scribere legionibus).

Quick answer

What is the Latin word for complement?: The usual Latin words for “complement” are complēmentum, refectiō, supplēmentum. The right choice depends on the sense; see the distinctions below.

Entry from J. E. Riddle & T. K. Arnold, A Copious and Critical English–Latin Lexicon (rev. C. Anthon, New York: Harper, 1864), digitised by Fergus J. P. Walsh, CC BY-SA 4.0; Latin markup adapted by latindictionary.co.