the act of placing together or bringing into proximity; juxtaposition.
the addition or application of one thing to another thing.
Grammar. a syntactic relation between expressions, usually consecutive, that have the same function and the same relation to other elements in the sentence, the second expression identifying or supplementing the first. In Washington, our first president, the phrase our first president is in apposition with Washington.
Biology. growth of a cell wall by the deposition of new particles in layers on the wall.