Foundation (2310) (themelios from théma = that which is laid down in turn from tÃthemi = to place [see study of related word themelioo]) means something laid or put down, that on which a structure is built or a stone used in the construction of a foundation. It was used literally of buildings foundation (foundation stone Rev 21:14). BDAG... 1 the supporting base for a structure, foundation - (a) of a stone that constitutes a foundation Rev 21:14; 19 (b) of the structural base for a building Lk 6:49, 14:29; on something Lk 6:48. The foundations of the heavenly city built by God He 11:10 [contrast ‘tents of Abraham’ with the city]). 2 the basis for something taking place or coming into being, foundation, fig. extension of meaning. (a) of the elementary beginnings of a thing; of the founding of a congregation Ro 15:20; 1Cor 3:10; 1Co 3:12. Of elementary teachings He 6:1. (b) of the indispensable prerequisites for something to come into being: God’s will is the foundation of an orderly creation. The foundation of the Christian church or congregation: Christ 1Co 3:11 became its foundation; the apostles and prophets Eph 2:20; cp. 2 Ti 2:19-note. (c) a foundation provides stability, therefore treasure, reserve 1 Ti 6:19 = ‘something fine to build on for the future’.—(Arndt, W., Danker, F. W., & Bauer, W. A Greek-English Lexicon of the New Testament and Other Early Christian Literature or Wordsearch) Thayer adds metaphorically, the foundations, beginnings, first principles, of an institution or system of truth (as what is necessary for belief or practice): 1Co 3:11, 12; the rudiments, first principles, of Christian life and knowledge, He 6:1; a course of instruction begun by a teacher, Ro 15:20...the Septuagint several times also for a palace (Isa 25:2, Je 6:5, Amos 1:4, etc). Themelios - 12x in 11v- Ro 15:20-note; 1Cor 3:10, 11, 12; Eph 2:20; 1Ti 6:19; 2Ti 2:19-note; Heb 6:1-note; He 11:10-note; Rev 21:14-note, Re 21:19-note NAS - foundation(11), foundation stone(1), foundation stones(2), foundations(2). Romans 15:20-note And thus I aspired to preach the gospel, not where Christ was already named, so that I would not build on another man's foundation; 1 Corinthians 3:10 According to the grace of God which was given to me, like a wise master builder I laid a foundation, and another is building on it. But each man must be careful how he builds on it. 11 For no man can lay a foundation other than the one which is laid, which is Jesus Christ. 12 Now if any man builds on the foundation with gold, silver, precious stones, wood, hay, straw, Ephesians 2:20 having been built on the foundation of the apostles and prophets, Christ Jesus Himself being the corner stone, 1 Timothy 6:19 storing up for themselves the treasure of a good foundation for the future, so that they may take hold of that which is life indeed. 2 Timothy 2:19-note Nevertheless, the firm foundation of God stands, having this seal, "The Lord knows those who are His," and, "Everyone who names the name of the Lord is to abstain from wickedness." Hebrews 6:1-note Therefore leaving the elementary teaching about the Christ, let us press on to maturity, not laying again a foundation of repentance from dead works and of faith toward God, Hebrews 11:10-note for he was looking for the city which has foundations, whose architect and builder is God. Revelation 21:14-note And the wall of the city had twelve foundation stones, and on them were the twelve names of the twelve apostles of the Lamb. Revelation 21:19-note The foundation stones of the city wall were adorned with every kind of precious stone. The first foundation stone was jasper; the second, sapphire; the third, chalcedony; the fourth, emerald; Themelios - 8x in the Septuagint - Deut 32:22; 1Ki 5:17; 2Ki 16:18; Ezra 4:12; 5:16; Job 22:16; Ps 87:1; 137:7 The foundation of the apostles and prophets - describes those of the NT era, first century AD. He does not mean the OT prophets for they knew nothing of the NT Church, the building that Paul is describing in this passage. Note carefully that although apostles and prophets are "foundational", they are not the ultimate foundation, which is Christ Himself. John MacArthur explains foundation of the apostles and prophets writing that... Because the Greek genitive case appears to be used in the subjective sense, signifying the originating agency, the meaning is not that the apostles and prophets were themselves the foundation—though in a certain sense they were—but that they laid the foundation. Paul spoke of himself as “a wise master builder” who “laid a foundation” and went on to say, “For no man can lay a foundation other than the one which is laid, which is Jesus Christ” (1Cor. 3:10, 11; cf. Ro 15:20-note). (MacArthur, J: Ephesians. Chicago: Moody Press)