[TrumanGrace]

In truth, they are synonyms. Colloquially, they have some differences in uses, but technically, the dictionary has similar definitions for them. So it's going to be for usage.

smart- intelligent, having a lot of knowledge. This is the guy who does well on research projects and such.

clever- quick witted. This is the guy who thinks better on the fly.

cleaver- a large, heavy knife such as one used by butchers to cut meat into joints or pieces. This is the thing that butchers wear chain-mail gloves to avoid cutting appendages off.