Fluency

Fluency: repeating or prolonging a sound when speaking

Types of Stuttering:

Repetitions - saying a whole word, part of a word, or a phrase more than one time (Ex. "I I I need to go to the bathroom.")
Blocks - no sound is produced and then a 'burst' of tension is released when the speaker is able to vocalize (Ex. "I want a -----cookie.")
Prolongations - holding on to a sound for an extended period of time (Ex. "I wwwwant to go to dinner.")
Revisions - speech is revised during an utterance (Ex. "I would like....I want a lemonade to drink.")
Interjections - adding extra words, such as: um, uh, like (Ex. "I, um, want pizza, uh, please.")

Reference:

This is the Stuttering Foundation's main website with great information for children and adults who stutter.
http://www.stutteringhelp.org/