Syntax
Syntax: The grammatical form of programs.
vs Semantics: The meaning of the program
Syntax (of textual languages) is typically specified by production rules for a context-free grammar using Backus-Naur Form (BNF) or Extended BNF (EBNF)
In visual languages, syntax is described by a set of restrictions on how diagrams may be constructed. (e.g., connection constraints)