Fillers
Fillers are parts of speech which are not generally recognized as purposeful or containing formal meaning, usually expressed as pauses such as uh, like and er, but also extending to repairs ("He was wearing a black—uh, I mean a blue, a blue shirt"), and articulation problems such as stuttering. Use is normally frowned upon in mass media such as news reports or films, but they occur regularly in everyday conversation, sometimes representing upwards of 20% of "words" in conversation. Fillers can also be used as a pause for thought ("I arrived at, um—3 o'clock").
Read more about this topic: Speech Disfluency