1. [n]  (linguistics) a distribution of related speech sounds or forms in such a way that they only appear in different contexts
2. [n]  the grammatical relation of a word or phrase to a predicate

COMPLEMENTATION is a 15 letter word that starts with C.

1. The ability of two unrelated single strands of DNA or RNA to pair with each other and become double stranded, due to the coincidental matching of an adequate number of nucleotide base pairs between the single strands.
2. In terms of genetics, the ability of one mutation to compensate for another, unrelated mutation. See also genetic complementation and cis-trans test.