Concise Bible Dictionary:
This word constantly occurs in the Old Testament in the sense of “the rest of the people.” In every crisis in the history of Israel there has been a remnant; this was seen in the time of Ahab (1 Kings 19:18), and so too in the introduction of Christianity (Luke 2:38), and that it will be so in the future is abundantly evident from the testimony of the prophets. There will be great prosperity in the land, and God will cause the remnant of His people to possess it (Zech. 8:12; compare Rev. 12:17). When God’s people are unfaithful to His calling, He secures His own purpose in a remnant.
The prophetic language in the Psalms is not that of the mass of Israel, but of the remnant, in whom the Spirit of Christ speaks; and it is in the Psalms that the remnant is first seen as distinguished from the ungodly nation. The idea of a remnant is found also in the address to the church in Thyatira, and to that remnant (“the rest”) it was said, “That which ye have already hold fast till I come” (Rev. 2:24-25). They represent the faithful in the time of the supremacy of the apostate Popish system.
A remnant represents morally the original whole, and does not imply an inferior remaining portion. It is of God’s grace that any are enabled to be steadfast to the original truth and calling during a general apostasy from it.
Strong’s Dictionary of Greek Words: