Which of the following best defines syntax?

The correct definition of syntax is indeed the structure of sentences. Syntax involves the rules and principles that govern the way words combine to create phrases and sentences in a language. This includes the arrangement of words, the relationship between them, and how they come together to convey meaning. Understanding syntax is crucial for sentence construction, as it affects clarity, coherence, and the overall flow of written and spoken language.

In contrast, the other options relate to different aspects of language. The meanings of words in context pertain to semantics, which is focused on interpretation rather than structure. Writing styles are concerned with individual author's voice and techniques rather than the grammatical composition of sentences. Phonetic pronunciations deal with the sounds of spoken language, rather than how those sounds are organized into grammatical structures. Each of these areas is important in the study of language, but they serve different purposes than understanding syntax specifically.