The current study measures laypeople's uses of um, uh, you know, and like, including folk notions of meanings, self-assessments of use, history of discussing use, and attitudes toward the words. Unlike the prevalent idea in the popular press that these discourse markers are interchangeable speaker production flaws, respondents in this study demonstrated that people do possess folk notions of meanings and uses that dramatically distinguish markers from each other. Um and uh were thought to indicate production trouble, you know was thought to be used in checking for understanding and connecting with listeners, and like defied definition. The folk notions of um, uh, and you know accord well with researchers' ideas about the meanings of these words. The use of like may be too subtle for laypeople to articulate. Most researchers' views of like involve some kind of discrepancy between what's said and what's meant. Even if they cannot state a meaning, people do treat the different markers differently.