(from the Hebrew word for "adversary") is a term that originates from the Abrahamic faiths, being traditionally applied to an angel in Judeo-Christian belief, and to a jinn in Islamic belief.
While Hebrew Ha-Satan is "the accuser" — the one who challenged the religious faith of humans in the books of Job and Zechariah — Abrahamic religious belief systems other than Judaism relate this term to a demon, a rebellious fallen angel, devil, minor god and idolatry, or as an allegory for evil.
'Satan' is שָׂטָן Satan in Standard Hebrew, Śāṭān in Tiberian Hebrew, סטנא Saṭänä in Aramaic, Σατανάς Satanás in Koine Greek, اهریمن Satanás in Persian, شيطان Šayṭān in Arabic, ሳይጣን Sāyṭān in Ge'ez, Şeytan in Turkish, and Shaitan शैतान in Hindi.
The Devil as seen in Codex Gigas.The word 'Satan', and the Arabic شيطان "shaitan", may derive from a Northwest Semitic root śṭn, meaning "to be hostile", "to accuse." An alternative explanation is provided by the Hebrew in Job 1:7. When God asks him whence he has come, Satan answers: "From wandering (mi'ŝuṭ) the earth and walking on it" (מִשּׁוּט בָּאָרֶץ, וּמֵהִתְהַלֵּךְ בָּה). The root ŝuṭ signifies wandering on foot or sailing. 'Satan' would thus be "the Wanderer".
As the "accuser"
Where Satan does appear in the Bible as a member of God's court, he plays the role of the Accuser, much like a prosecuting attorney for God.
According to the article on 'Satan' in the Jewish Encyclopedia, Satan's role as the accuser is found
“ in the prologue to the Book of Job, where Satan appears, together with other celestial beings or 'sons of God,' before the Deity, replying to the inquiry of God as to whence he had come, with the words: 'From going to and fro in the earth, and from walking up and down in it.' (Job 1:7) Both question and answer, as well as the dialogue which follows, characterize Satan as that member of the divine council who watches over human activity, but with the evil purpose of searching out men's sins and appearing as their accuser. He is, therefore, the celestial prosecutor, lawyer who sees only iniquity; for he persists in his evil opinion of Job even after the man of Uz has passed successfully through his first trial by surrendering to the will of God, whereupon Satan demands another test through physical suffering. (ib. ii. 3-5.) ”
“ Yet it is also evident from the prologue that Satan has no power of independent action, but requires the permission of God, which he may not transgress. He cannot be regarded, therefore, as an opponent of the Deity; and the doctrine of monotheism is disturbed by his existence no more than by the presence of other beings before the face of God. This view is also retained in Zech. 3:1-2, where Satan is described as the adversary of the high priest Joshua, and of the people of God whose representative the hierarch is; and he there opposes the 'angel of the Lord' who bids him be silent in the name of God. ”
“ In both of these passages Satan is a mere accuser who acts only according to the permission of the Deity; but in I Chron. 21:1 he appears as one who is able to provoke David to destroy Israel. The Chronicler (third century B.C.) regards Satan as an independent agent, a view which is the more striking since the source whence he drew his account (II Sam. 24:1) speaks of God Himself as the one who moved David against the children of Israel. Since the older conception refers all events, whether good or bad, to God alone, (I Sam. 16:14; I Kings 22:22; Isa. 45:7; etc) it is possible that the Chronicler, and perhaps even Zechariah, were influenced by Zoroastrianism, even though in the case of the prophet Jewish monism strongly opposed Iranian dualism. (Stave, Einfluss des Parsismus auf das Judenthum, pp. 253 et seq.) An immediate influence of the Babylonian concept of the 'accuser, persecutor, and oppressor' (Schrader, K. A. T. 3d ed., p. 463) is impossible, since traces of such an influence, if it had existed, would have appeared in the earlier portions of the Bible."