Boyd’s Bible Dictionary:

A short, two-edged, dagger-like weapon, carried in a sheath or scabbard, and suspended to the girdle or belt
(Gen. 27:40; Judg. 3:16; 2 Sam. 20:8; Jer. 47:6; Ezek. 21:9,30).

Concise Bible Dictionary:

This is constantly referred to in scripture as the instrument of death, and is mentioned in the New Testament as being borne by the magistrate (Rom. 13:4), showing that the gospel does not set aside God’s governmental principle of capital punishment which was enjoined after the flood (Gen. 9:5-6). See Armor, ARMS.
SWORD OF THE SPIRIT. This is the word (ρῆμα) of God, what His mouth has spoken, and is the only offensive weapon given to Christians with which to fight the Lord’s battles (Eph. 6:17). The word (λόγος) of God is likened to a two-edged sword (Heb. 4:12), and the words of the Lord Jesus when He will come forth in judgment on Christendom and the world are compared to a “sharp two-edged sword” (Rev. 1:16; Rev. 19:15).

From Manners and Customs of the Bible:

1 Samuel 17:39. David girded his sword upon his armor, and he assayed to go.
The sword was one of the earliest weapons in use. The Egyptian sword was short and straight, two and a half to three feet long, and double-edged. The handle was plain and hollowed in the center, the better to afford a firm grasp. The Hebrew sword probably resembled it.