The Switchboard corpus of American English telephone conversations between strangers was collected in the early 1990s; it contains 2430 conversations averaging 6 minutes each, totaling 240 hours of speech and about 3 million words (Godfrey et al., 1992) . Such corpora of spoken language don't have punctuation but do intro-duce other complications with regard to defining words. Let's look at one utterance from Switchboard; an utterance is the spoken correlate of a sentence: I do uh main-mainly business data processing This utterance has two kinds of disfluencies. The broken-off word main-is disfluency called a fragment. Words like uh and um are called fillers or filled pauses. Should we consider these to be words? Again, it depends on the application. If we are building a speech transcription system, we might want to eventually strip out the disfluencies.