Discourse marker

A discourse marker is a word or phrase that does not significantly change the meaning of the sentence, but which can, among other functions, "show the connection between what a speaker is saying and what has already been said or what is going to be said.

Examples include "oh", "well", "now", "then", "you know", and "I mean".

In Practical English Usage (1980), Michael Swan divides the most common ones into 21 groups, such as "focusing and linking" (as regards, as for); "balancing contrasting points" (on the other hand, while); "emphasising a contrast" (however, still, yet); "logical consequence" (so, then).