The description of sentences in TGG is based on the operation of several types of rules which constitute the components of grammar. It is important to note that there are differences between the two versions of TGG, the Classical Theory of 1957 and the Standard Theory of 1965, in the types, the number, the status and the order of components.
Morphophonemic rules are a set of rules that turn the symbols in terminal strings (the abstract morphemes) into phonological representations of their actual spoken form (strings of phonemes or actual phonetic sounds).