A syntactic category is either a phrasal category , such as noun phrase or verb phrase, which can be decomposed into smaller syntactic categories, or a lexical category, such as noun or verb, which cannot be further decomposed.
In terms of phrase structure rules, phrasal categories can occur to the left side of the arrow while lexical categories cannot.
The lexical categories are traditionally called the parts of speech. They include nouns, verbs, adjectives, and so on.
See also
