It is never a good idea to leave a person who suffers from pyromania alone with a box of matches, since pyromania is a strong urge to start fires.
Manias, compulsions or obsessions, are rarely good things, and this one is especially undesirable: an uncontrollable impulse to set fires. The pyr- part, from Greek for "fire," appears in pyramid, pyrotechnic, and empyreal; the English word fire is also distantly related. The mania part means "madness" in Greek, and "fire madness" is a good way to think of pyromania.
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