Impel vs Compel

Impel is very similar in meaning to compel, and often a perfect synonym, though it tends to suggest even more strongly an inner drive to do something and a greater urgency to act, especially for moral reasons. But when impel takes its noun and adjective forms, it changes slightly. So an impulse—such as "impulse buying", when you suddenly see something cool and know you've got to have it—often isn't based on anything very serious. And impulsive behavior in general, such as blurting out something stupid on the spur of the moment, is the kind of thing you're supposed to get over when you grow up.