This paper is an attempt to clarify the status of discourse markers. These lexical expressions have been studied under various labels, including discourse markers, discourse connectives, discourse operators, pragmatic connectives, sentence connectives, and cue phrases. Although most researchers agree that they are expressions which relate discourse segments, there is no agreement on how they are ... [Show full abstract] to be defined or how they function.After reviewing prior theoretical research, I define discourse markers as a class of lexical expressions drawn primarily from the syntactic classes of conjunctions, adverbs, and prepositional phrases. With certain exceptions, they signal a relationship between the interpretation of the segment they introduce, S2, and the prior segment, S1. They have a core meaning, which is procedural, not conceptual, and their more specific interpretation is ‘negotiated’ by the context, both linguistic and conceptual. There are two types: those that relate the explicit interpretation conveyed by S2 with some aspect associated with the segment, S1; and those that relate the topic of S2 to that of S1. I conclude by presenting what appears to be the major classes according to their function.