This thesis is concerned with developing a syntax for coordinate structures which is compatible with both the syntactic behaviour of conjunction structures and with their semantics. It argues that coordinate structures are asymmetrical, hierarchical structures that conform with X-bar theory. The conjunction head projects a phrase which is adjoined to the first conjunct. This provides an account of a number of syntactic asymmetries in conjunct ordering including agreement and binding asymmetries and provides a principled analysis of Across-the-Board extraction as instances of parasitic gaps. It further argues that the Coordinate Structure Constraint cannot be a syntactic constraint, but rather must be a condition on conjoining identical semantic categories. This provides an account of unlike category coordination which is shown to be freely possible if semantic identity is preserved and no independent syntactic constraints are violated, a result which follows from the adjunct nature of the coordinate structure. In order to account for the semantic identity, it is proposed that at Logical From, each conjunct is a predicate in an identification relation with the conjunction head, which raises to take scope over all the conjuncts. Assuming theta role assignment at LF, only the conjunction head receives a theta role; none of the conjuncts does. Because each conjunct is in a predication relation with the conjunction head at LF, the semantic identity constraint follows directly. The fact that the conjuncts do not receive a theta role accounts for their inability to act as antecedents for reflexive binding and for the fact that modal adverbs can appear inside conjoined NPs. The proposed analysis assimilates coordinate structures directly to plurals, and argues that a consequence of the proposed LF is that all natural language conjunction and disjunction is group forming rather than propositional. All semantic ambiguities between distributed and collective coordination can then be derived with the appropriate logical representation for plurals in general, rather than having a separate semantics altogether for coordination.