What major development occurs during the fifth stage of first-language acquisition?

The fifth stage of first-language acquisition is marked by the emergence of characteristic grammatical structures. During this stage, which typically occurs between the ages of two and a half to three years, children begin to formulate more complex sentences and demonstrate a better understanding of grammar rules. They start to combine words into phrases and sentences that reflect their growing grasp of language structure, such as the use of plurals, past tense, and basic grammatical connectors. This demonstrates a significant shift from merely using isolated words or simple phrases to constructing more meaningful and syntactically correct utterances.

In contrast, while phonetic development occurs earlier in language acquisition, it is not the primary focus during this later stage. Non-verbal communication is foundational and developed much earlier in infancy, and reinforcement of simple phrases relates more to earlier stages where children typically mimic language. Thus, the emergence of characteristic grammatical structures represents a critical milestone in a child's linguistic development, showcasing their advancing cognitive abilities and increasing proficiency in their native language.