From The Free On-line Dictionary of Computing: (http://www.foldoc.org/, Editor Denis Howe)
The structure of strings in some language. A language's syntax is described by a grammar. For example, the syntax of a binary number could be expressed as
binary_number = bit [ binary_number ]
bit = "0" | "1"
meaning that a binary number is a bit optionally followed by a binary number and a bit is a literal zero or one digit.
The meaning of the language is given by its semantics.