Within the great collection of things that have been labeled "particles", we find at least one grammatically significant class of items, in English and in languages generally. These have been variously termed "discourse particles" and "interjections"; here I will call them "discourse markers". On the ground of distribution, prosody, and meaning, discourse markers can be seen to form a class. [...] they are independent words rather than clitics [...]. The Eng. discourse markers, some of which have been discussed recently by James [James, Deborah, 1974, The syntax and semantics of some English interjections, University of Michigan papers in linguistics, Ann Arbor], Goldberg [Goldberg, Julia, 1980, Discourse partcles: An analysis of the role of “y’know”, “I mean”, “well”, and “actually” in conversation, Doctoral dissertation, Cambridge University], and Shourup [Shourup, Lawrence, 1983, Common discourse particles in English conversation, Ohio State University working papers in linguistics, 28, Columbus], include (certain instances of) "well, hey, okay, oh yes, like, y'know, no, uh now, say, why, look", listen, and "please" [...].
- Zwicky (2004), a pag.372