The term Ha-Satan is a Hebrew word used to describe a definite adversary (as in Zecharia 3:1-2,).
The word Satan is a derivative of Ha-Satan.
Judaism has no devil, there is no embodiment of evil who tempts them. This is in contrast to the Christian idea of Satan. In Christianity, Satan is often viewed as a type of demi-god who plays an active part in man's salvation (usually by attempting to destroy it). Satan is often pinpointed as being the source of evil in the world. Both Satan and God are often displayed as being anthropomorphic (usually a couple of guys).
If, however, one were to claim that there are other beings that have powers greater than mankind's (such as Satan, demons, angels) that act on behalf of their own volition or an all-powerful god, we must ask ourselves, is this truly monotheistic?
Certainly the Jewish faith ascertains that there is only one god and no entity that can compare, but what of Christianity then? Surely this faith concludes that there is only one god, however, any preternatural beings illustrated in the New Testament would indeed by god-like.
Although not polytheistic, arguments can be supported that the Christian religion is actually henotheistic rather than monotheistic in nature. According to Webster's online dictionary, henotheisim is the worship of one god without denying the existance of other gods. If one were to view these beings in a context outside of the Christian mythos, they would indeed be gods of a lesser nature. No doubt Zeus was more powerful than Athena, yet Athena more powerful than mankind.