Meaning

noun a grammatical relation between a word and a noun phrase that follows

noun (biology) growth in the thickness of a cell wall by the deposit of successive layers of material

noun the act of positioning close together (or side by side)

originFrom Middle English apposicioun, from Middle French apposition, from Latin appositiō, past participle of appōnere (“to put near”).

Etymology from Wiktionary, CC BY-SA 3.0