Syntactic theory and first language acquisition

The analysis focuses on the speech development of a 26-month-old child, Heather, who has progressed to the multi-word stage. It highlights her use of three primary functional category systems: the D-system, I-system, and C-system. The paper explores the X-bar model, which posits that any word category can serve as the head of a phrase and can be expanded into a corresponding phrasal category through the addition of modifiers such as complements, adjuncts, and specifiers, ultimately detailing the structure of English phrases.