From suniemi; a mental putting together, i.e. Intelligence or (concretely) the intellect -- knowledge, understanding.
see GREEK suniemi
1. a running together, a flowing together: of two rivers, Homer, Odyssey 10, 515.
2.
a. from Pindar down, understanding: Luke 2:47; 1 Corinthians 1:19 (from Isaiah 29:14); Ephesians 3:4; Colossians 2:2; 2 Timothy 2:7; πνευματικῇ, Colossians 1:9.
b. the understanding, i. e. the mind so far forth as it understands: Mark 12:33; Wis. 4:11. (The Sept. for בִּינָה, תֲּבוּנָה, דַּעַת, מַדַע , שֵׂכֶל, etc.; also for מַשׂכִיל, a poem.) (Synonym: see σοφία, at the end; cf. Lightfoot on Colossians 1:9; Schmidt, chapter 147, 8.)