This paper discusses six formalization techniques, of varying strengths, for extending a formal system based on traditional mathematical logic. The purpose of these formalization techniques is to simulate the introduction of new syntactic constructs, along with associated semantics for them. We show that certain techniques (among the six) subsume others. To illustrate sharpness, we also consider a selection of constructs and show which techniques can and cannot be used to introduce them. The six studied techniques were selected on the basis (...) of actual practice in logic and computing. They do not form an exhaustive list. (shrink)