sentences:  Merge is assumed to have certain formal properties constraining syntactic structure, and is implemented with specific mechanisms.In terms of a merge-base theory of language acquisition, complements and specifiers are simply notations for first-merge (= "complement-of" [head-complement]), and later second-merge (= "specifier-of" [specifier-head], with merge always forming to a head.First-merge establishes only a set {a, b} and is not an ordered pair--e.g., an {N, N}-compound of 'boat-house' would allow the ambiguous readings of either 'a kind of house' and/or 'a kind of boat'.