This word (in the singular or plural) is used in the Old Testament to render different Hebrew words. In thirty-two cases the word corresponds to the noun tsar, or the verb tsarar. This noun is the ordinary word for "foe" or "adversary." In twelve passages the Hebrew word, of which "adversary" is the translation, is saTan = noun or saTan = verb. This stem means "to oppose," or "thwart" anyone in his purpose or claims.
The angel of Yahweh was saTan to Balaam (Numbers 22:22). The word often denotes a political adversary (1 Kings 11:14,23,25). In four cases (namely, Prologue to Job; Zechariah 3:1,2; 1 Chronicles 21:1; Psalms 109:6) the King James Version retains Satan as the rendering. But it is only in 1 Chronicles that the word is used without the article, that is, strictly as a proper name. The Septuagint gives diabolos, as the rendering, and both in Job and Zechariah, Satan is portrayed as the "false accuser." In two cases "adversary" represents two Hebrew expressions which mean the "opponent in a suit" or "controversy" (Job 31:35; Isaiah 50:8).
In the New Testament "adversary" represents:
(1) antikeimenoi, the participle of a verb which means "to be set over against," "to be opposed" (Luke 13:17; Philippians 2:8).
(2) antidikos, "opponent in a lawsuit," "prosecutor" (Matthew 5:25; Luke 12:58; 18:3; 1 Peter 5:8).
According to the last passage the devil is the "accuser" or "prosecutor" of believers, but according to another writer they have an "advocate" or "counselor for the defense" with the Father (1 John 2:1). In one passage (Hebrews 10:27) "adversary" represents a Greek word, hupenantios, which means "set over against," "contrary to"--a word used in classical Greek and in the Septuagint.