Apposition

noun

1. (grammar) A construction in which one noun or noun phrase is placed with another as an explanatory equivalent, both of them having the same syntactic function in the sentence.
2. The relationship between such nouns or noun phrases.
3. The quality of being side-by-side, apposed instead of being opposed, not being front-to-front but next to each other.
4. A placing of two things side by side, or the fitting together of two things.
5. In biology, the growth of successive layers of a cell wall.