There is a great deal of confusion about the term 'grammar'. Most people associate with it a book written about a language. In fact, there are various manifestations of this traditional term: presecriptive, descriptive and reference grammar. In theoretical linguistics, grammars are theory-based coherent systems of rules and principles which model a speaker's knowledge of language. These formal grammars combine insights from all branches of linguistics, with syntax in the center.This e-lecture discusses the different approaches towards the term grammar.