Greek hē ampelos hē alēthinē — "the vine, the true one." The last of Jesus' seven "I AM" statements in John (John 15:1). The vine was Israel's national symbol, stamped on temple gates and coins, and the OT repeatedly figures Israel as Yahweh's vineyard (Isaiah 5:1-7, Psalm 80:8-16, Jeremiah 2:21) — planted, tended, and disappointingly wild. Jesus' word alēthinē ("true, real, genuine") implicitly contrasts Himself with Israel-the-failed-vine. He is the vine Israel was meant to be.
The True Vine discourse is the deepest NT picture of the believer's union with Christ. We are not partners, employees, or even servants — we are branches, with no life of our own. "Abide in Me, and I in you. As the branch cannot bear fruit by itself, unless it abides in the vine, neither can you, unless you abide in Me" (John 15:4). The Father is the Vinedresser; He prunes every fruit-bearing branch so it bears more fruit — which is why sanctification often feels like cutting. Fruitless branches (pretenders, not believers) are gathered and burned. Much fruit, we're told, glorifies the Father (15:8). The sap is the Spirit; the fruit is the fruit of the Spirit (Galatians 5:22-23); the gardening hurts but is love.