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What is the difference between impel and compel?

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To me, impel has a sense of motion/pushing, while compel is more of an obligation. Think of impulse vs. compulsion.

There's also a difference in origin: with impel, the primary force comes from within the object (albeit in response to an outside impetus), while compel comes from outside and acts on the object. I can compel you to do something, but I can only cause you to feel impelled. Or something like that.

6

To impel is to push someone or something forward, while to compel is to force someone to do something. The difference is subtle, but usually compel carries a connotation of coercion or obligation. Impel has its roots in the Latin word for "to push forward", while compel comes from that for "to drive together".