1. A syntax defines the rules and structure of proper sentences through word order and grammatical categories like nouns, verbs, adjectives. 2. Key parts of syntax include noun phrases (NP), verb phrases (VP), prepositions (PP), and formulas to define sentence structure like S → NP + VP. 3. Main lexical categories include nouns (people, places, things), pronouns (words used instead of nouns), verbs (words describing actions), adjectives (words describing nouns), adverbs (words adding meaning to verbs/adjectives), and determiners (words specifying nouns like articles).