A patient describes a repetitive urge and an accompanying repetitive action. Before revealing the answer, decide what distinguishes a compulsion from an obsession.

Ask whether you are describing the thought or urge itself, or the behaviour carried out because of it. An obsession is the intrusive thought, image, or urge itself — unwanted but recognised as the person's own — while a compulsion is the behavioural, motor expression of that underlying urge or fear, the repetitive action performed in response to it. The two frequently occur together, with the compulsion often serving to relieve the anxiety generated by the obsession, but they are conceptually distinct: one is a disturbance of thought content, the other of motor behaviour arising from it.