A deictic expression is a linguistic term that refers to words or phrases that depend on the context in which they are used, often pointing to specific entities, times, or locations. These expressions require contextual information to convey their meaning, as they can vary depending on who is speaking, where the conversation is happening, and when it takes place. Common examples include pronouns like 'I' and 'you', demonstratives such as 'this' and 'that', and temporal references like 'now' and 'then'.