In this paper we present the design and specification of a family of syntax definition formalisms. The kernel of this family of formalisms is formed by context-free grammars. A number of orthogonal extensions to the kernel is defined. Many of these extensions are defined in terms of the primitives of the kernel by means of normalization functions. This provides a framework for constructing new formalisms by adapting and extending previous ones. Included in the family are the following extensions of context-free grammars: uniform definition of lexical and context-free syntax, variables, disambiguation by priorities, follow restrictions and reject productions, a rich set of regular expressions defined in terms of context-free productions, character classes, aliases, parameterized modules with hidden imports and renamings. The accumulation of these extensions is the syntax definition formalism SDF2.