Which of the following describes a linguistic feature that may change depending on the context of communication?

Language register refers to the variations in language used in different contexts or situations. It includes factors such as formality, tone, and vocabulary choices adapted to the audience or purpose of communication. For example, the way one might speak in a formal presentation is different from how one would converse with friends in a casual setting. Context can influence the register significantly—one may choose a more academic language in a scholarly article compared to the informal chat that occurs in a social environment.

The other options present aspects of language that are less flexible with regard to context. Grammar relates to the rules governing the structure of sentences and does not change based on context in the same way that register does. Semiotics, the study of signs and symbols in communication, provides insights into meaning but does not directly account for how language use changes with different social situations. Phonology, which deals with the sound systems of languages, is relatively stable regardless of the communicative context. Thus, language register is the feature that most explicitly adapts to different communicative situations, making it the correct choice.