Hebrew: "mal'ak" / Greek: "aggelos."
In both languages, the word means "messenger," and is used to describe any agent God sends to do his will. It does not always refer to heavenly beings.
For much more information about angels, see our answer to "What does the Bible Say about angels?"
The appearances of "the Angel of the Lord" to Abraham at Mamre (Gen. 18:2, 22. Compare 19:1), to Jacob at Peniel (Gen. 32:24, 30), to Joshua at Gilgal (Josh. 5:13,15), were of the pre-incarnate Jesus Christ. They were "foreshadowings of the incarnation," revelations before the "fullness of the time" of the Son of God.
These superior beings are very numerous. "Thousand thousands," etc. (Dan. 7:10; Matt. 26:53; Luke 2:13; Hebrews 12:22-23). They have different ranks in dignity and power (Zech. 1:9,11; Dan. 10:13; 12:1; 1 Thess. 4:16; Jude 1:9; Eph. 1:21; Col. 1:16).
They are spirits (Hebrews 1:14), like the soul of man, but without a physical body.
Such expressions as "like the angels" (Luke 20:36), and the fact that whenever angels appeared to man it was always in a human form (Gen. 18:2; 19:1, 10; Luke 24:4; Acts 1:10), and the titles that are applied to them ("sons of God," Job 1:6; 38:7; Dan. 3:25; compare 28) and to men (Luke 3:38), all seem to indicate some resemblance between them and the human race.
Imperfection is ascribed to them (Job 4:18; Matt. 24:36; 1 Pet. 1:12). As free-willed creatures, they may fall under temptation; and thus we read of "fallen angels." We can only guess at the cause and manner of their "fall." We know only that fallen angels "left their first estate" (Matt. 25:41; Rev. 12:7,9), and that they are "reserved unto judgement" (2 Pet. 2:4).
Angels never die (Luke 20:36). They possess superhuman intelligence and power (Mark 13:32; 2 Thess. 1:7; Ps. 103:20).
They are called "holy" (Luke 9:26), "elect" (1 Tim. 5:21). The redeemed in glory are "like the angels" (Luke 20:36).
They are not to be worshipped (Col. 2:18; Rev. 19:10).
They have many functions.
In the widest sense, they are AGENT'S OF GOD'S PROVIDENCE (Ex. 12:23; Ps. 104:4; Hebrews 11:28; 1 Cor. 10:10; 2 Sam. 24:16; 1 Chr. 21:16; 2 Kings 19:35; Acts 12:23).
They are especially God's agents in carrying on his great WORK OF REDEMPTION. There is no clear report of angelic appearances to man till after the call of Abraham. From that time onward there are frequent references to their ministry on earth (Gen. 18; 19; 24:7, 40; 28:12; 32:1). They appear to rebuke idolatry (Judg. 2:1-4), to call Gideon (Judg. 6:11-12), and to consecrate Samson (13:3). In the days of the prophets, from Samuel downward, the angels appear only on their behalf (1 Kings 19:5; 2 Kings 6:17; Zech. 1-6; Dan. 4:13, 23; 10:10,13, 20-21).
When Jesus Christ came to earth to die, a new era was begun in the ministry of angels. They came with their Lord to earth to assist him while here. They predict his advent (Matt. 1:20; Luke 1:26-38), minister to him after his temptation and agony (Matt. 4:11; Luke 22:43), and declare his resurrection and ascension (Matt. 28:2-8>; John 20:12-13; Acts 1:10-11).
They now minister to the people of God (Hebrews 1:14; Ps. 34:7; 91:11; Matt. 18:10; Acts 5:19; 8:26; 10:3; 12:7; 27:23). They rejoice over a repentant sinner (Luke 15:10). They carry the souls of the redeemed to paradise (Luke 16:22); and they will be the ministers of judgement on the great day of judgement (Matt. 13:39,41, 49; 16:27; 24:31).
GUARDIAN ANGELS? - The passages (Ps. 34:7, Matt. 18:10) usually referred to in support of the idea that every individual has a particular guardian angel have no such meaning. They merely indicate that God employs the ministry of angels to deliver his people from affliction and danger, and that the angels do not think it below their dignity to minister even to children and to the least among Christ's disciples.
ANGEL OF HIS PRESENCE - The "angel of his presence" (Isa. 63:9. Compare Ex. 23:20-21; 32:34; 33:2; Num. 20:16) sometimes referred to in the Bible is probably referring to the Messiah as the guide of his people. Others have supposed the expression to refer to Gabriel (Luke 1:19).
When the manna is called "angels’ food" in Psalms, this is merely to describe its heavenly excellence (Psalm 78:25).