from humanities.org
What is the Difference Between a Moron, Imbecile and Idiot?
It's true — there's a difference. The three terms didn't start out as social insults either, in fact. In the early 1900s, psychologists used the terms to describe various levels of retardation. Those with an IQ of 0 to 25 (an IQ of 100 is average) were called idiots, 26 to 50 were called imbeciles and 51 to 70 were called morons. Morons could communicate and learn common tasks; imbeciles stalled mentally at about six years old; and idiots couldn't respond to stimulus or communicate with any level of competency.
no matter what i say, i don't think anyone on even this board is an idiot.
the only use of "imbecile" in a sentence might be a quote from moe howard
i guess that leaves "moron ...." barely communicate and complete simple tasks