Aphasia is a primary disorder of language resulting from brain injury.  The language impairment that is common to all aphasic patients--at least at some point during the course of their aphasia--is an abnormal difficulty retrieving words.  Some patients with aphasia produce sentences of normal length and prosody; we characterize their output as being fluent.  Other patients with aphasia produce pieces of sentences, the output is short and choppy, phrase length is reduced to one or two words, and speech is halting, with many pauses.  The speech of these patients is defined as being nonfluent.  Fluency, then, is defined chiefly with regard to phrase length.