Speed - e.g. racing thoughts in mania
Flow and coherence:
Loose associations - moving rapidly between topics with no apparent connection
Circumstantial - irrelevant details
Tangential - digressions from main subject
Flight of ideas - fast, pressured speech with ideas running into one another
Thought blocking - sudden cessation of thought
Perseveration - repetition of a response despite the removal of the stimulus
Neologisms - makes up words
Word salad - random string of words without relation