Circumstantiality is the inability to answer a question without giving excessive, unnecessary detail. However, this differs from tangentiality in that the person does eventually return to the original point.
Tangentiality refers to wandering from a topic without returning to it.
Neologisms are new word formations, which might include the combining of two words.
Clang associations are when ideas are related to each other only by the fact they sound similar or rhyme.
Word salad describes completely incoherent speech where real words are strung together into nonsense sentences. (see: Wernicke’s aphasia)
Knight's move thinking is a severe type of loosening of associations, where there are unexpected and illogical leaps from one idea to another. It is a feature of schizophrenia.
Flight of ideas, a feature of mania, is a thought disorder where there are leaps from one topic to another but with discernible links between them.
It is important to be able to distinguish flight of ideas from Knight's move thinking, as flight of ideas is associated with mania whilst Knight's move is associated with schizophrenia. In flight of ideas, there are discernible links between the topics that the patient jumps between, whilst in Knight's move thinking there are no discernible links between the topics that the patient jumps between in conversation. This is known as loosening of association.
Perseveration is the repetition of ideas or words despite an attempt to change the topic.
Echolalia is the repetition of someone else's speech, including the question that was asked.