The rules by which parts may be joined to make sense. Syntax governs arrangement, not meaning.
Greek σύνταξις (syntaxis, a putting together in order), from syn (together) + tassein (to arrange); the rules by which parts may be joined govern only their arrangement, never what they mean once arranged.
The rules by which parts may be joined to make sense. Syntax governs arrangement alone, and never decides meaning by itself.