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complement

/ˈkɑmpləmənt/

Something that completes, fills, or enhances another

From Latin com- (together) + Latin plēre (to fill).

noun
verb
com-
Latin
Verified
com-
Intensive prefix meaning 'altogether' or 'thoroughly'; in this word, probably strengthens the idea of filling.

from Old French compliement "accomplishment, fulfillment" (14c., Modern French complément )

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plēre
Latin
AI-inferred
plēre
Verb meaning 'to fill'; source of the completion sense in complementum.
Combined
complementum
Latin noun meaning 'that which fills up or completes,' formed from com- plus plēre.
Old French
Verified
compliement
Meaning 'accomplishment' or 'fulfillment.'

from Old French compliement "accomplishment, fulfillment" (14c., Modern French complément )

Middle English
Verified
complement
Borrowed into English in the late 14th century.

from Latin complementum "that which fills up or completes,"

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Modern English
Verified
complement
Extended to a full amount, a completing partner, mathematical remainder, and biological immune-system proteins.

from Latin complementum "that which fills up or completes,"

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Modern English
complement

Picture a Roman clerk filling a measure to the brim: that simple act of making something whole lies behind Latin complementum, “that which fills up or completes.” The word reached English through Old French compliement and Middle English, arriving in the late 14th century with the practical sense of whatever supplies the missing piece. Its family has some wonderfully visible cousins: full, plenty, plenary, and replete all carry the same old image of abundance, while complete is its close double. By the 1870s, complement had wandered into music, where one interval “fills” another to make an octave; mathematics later used it for what lies outside a set, and biology gave the word to blood proteins that help complete an immune attack. The spelling split produced a famous trap: a complement completes you, while a compliment merely flatters you—but both began life close enough to be linguistic twins.

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