What's the difference between parkinsonism and parkinson's syndrome?

Variation on a theme: Parkinson's disease (pd) is a neurodegenerative disorder of as yet unknown cause, which has typical symptoms including tremor, stiffness, lack of spontaneous movement (and many others). Parkinsonism is a condition in which some of the factors of true pd are present but atypical factors are also present. Commonest form is drug-induced parkinson-like movement disorder.