Discourse markers come from varied word classes, such as adverbs (well) or prepositional phrases (in fact).
The process that leads from a free construction to a discourse marker can be traced back through grammaticalization studies and resources.
[citation needed] Discourse markers can be seen as a “joint product” of grammaticalization and cooption, explaining both their grammatical behavior and their metatextual properties.
Now they are assigned functions in different levels of analysis: topic changes, reformulations, discourse planning, stressing, hedging, or backchanneling.
Yael Maschler divided discourse markers into four broad categories: interpersonal, referential, structural, and cognitive.