This paper presents a general framework for mechanism synthesis based on analysis and synthesis operators. Examples of both exact synthesis and approximate synthesis arc given and the synthesis of mechanisms via optimization techniques is explained using synthesis and analysis operators. Synthesis is addressed as a mapping from the space M of rigid body motions to the space (T,D) of mechanism types and dimensions. Among the results of this formulation are an identification of cognates as mechanisms with the value t of type held constant but with a different vector of dimensions d such that the same motion m is generated. A discussion of this formulation is given, optimal mechanism synthesis is re-interpreted within this framework and some avenues for further work which are indicated by this framework are identified.