Discourse marker
A discourse marker is a word or phrase that is relatively syntax-independent and does not change the truth conditional meaning of the sentence, and has a somewhat empty meaning. Examples of discourse markers include the particles "oh", "well", "now", "then", "you know", and "I mean", and the discourse connectives "so", "because", "and", "but", and "or".
In Practical English Usage Michael Swan defines a 'discourse marker' as 'a word or expression which shows the connection between what is being said and the wider context'. For him, a discourse marker is something that either connects a sentence to what comes before or after, or indicates a speaker's attitude to what he is saying. He gives three examples: on the other hand; frankly; as a matter of fact.
Traditionally, some of the words or phrases that were considered discourse markers were treated as "fillers" or "expletives": words or phrases that had no function at all. Now they are assigned functions in different levels of analysis: topic changes, reformulations, discourse planning, stressing, hedging, or backchanneling. Those functions can be classified into three broad groups: (a) relationships among (parts of) utterances; (b) relationships between the speaker and the message, and (c) relationships between speaker and hearer. An example of the latter is the Yiddish involvement discourse marker nu, also used in Modern Hebrew and other languages, often to convey impatience or to urge the hearer to act (cf. German cognate nun, meaning "now" in the sense of "at the moment being discussed," but contrast Latin etymological cognate nunc, meaning "now" in the sense of "at the moment in which discussion is occurring"; Latin used iam for "at the moment being discussed," and German uses jetzt for "at the moment in which discussion is occurring").
