a. A construction in which a noun or noun phrase is placed with another as an explanatory equivalent, both having the same syntactic relation to the other elements in the sentence; for example, Copley and the painter in The painter Copley was born in Boston.
b. The relationship between such nouns or noun phrases.
2. A placing side by side or next to each other.
3. Biology The growth of successive layers of a cell wall.
[Middle English apposicioun, from Latin appositiō, appositiōn-, from appositus, past participle of appōnere, to put near; see APPOSITE.]
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