Syntax is the set of rules that govern how words combine into phrases and sentences. These rules determine that “The cat chased the mouse” is well-formed while “Chased the cat mouse the” is not. Syntax is distinct from meaning; a sentence can be grammatical yet nonsensical, as in Chomsky’s famous example “Colorless green ideas sleep furiously.”

Languages differ dramatically in their syntactic systems. Some rely heavily on word order; others use rich systems of case markings. Yet all human languages appear to share certain abstract design features, a fact that has fueled theories of an innate universal grammar.

Children acquire the syntax of their native language with little explicit instruction, typically mastering the core patterns by age four or five. Syntactic knowledge is largely unconscious; speakers can judge sentences as grammatical or not without being able to state the rules they are applying.

• Rules for combining words into sentences
• Independent of semantic content
• Varies across languages yet shows universal properties
• Acquired early and largely implicitly

Disorders that selectively impair syntactic processing provide further evidence that grammar constitutes a distinct component of the language system.