What language skill is an 18-month-old child likely to develop next after acquiring a one-word vocabulary?

An 18-month-old child typically progresses to the use of two-word sentences after establishing a one-word vocabulary. This developmental stage marks a significant shift in language acquisition, allowing children to express more complex ideas and relationships.

At this age, children begin to combine words to convey meanings more clearly, such as pairing nouns with verbs (e.g., "want cookie" or "go park"). This ability reflects not only their expanding vocabulary but also their understanding of how words can interact to form simple sentences. This foundational skill in language development is critical as it paves the way for more advanced language abilities, including grammar, syntax, and storytelling as they grow older.

The other options reflect concepts that are generally developed later. For instance, responding to indirect requests and recognizing grammatical structures involve a more mature understanding of language that typically appears as children approach the age of three or older. Similarly, modifying speech for the listener involves social awareness and pragmatic skills that are also developed later in childhood; they require a level of cognitive and linguistic maturity that emerges beyond the 18-month mark.