συν-ίημι and συνίω (see Bl. § 23, 7),

[in LXX chiefly for בִּין hi. שָׂכַל hi. ;]

__1. to bring or set together.

__2. Metaphorical, to perceive, understand: Mat.13:13-15 (LXX), Mat.13:19 15:10, Mrk.4:9 (WH, mg.), Mrk.4:12 7:14 8:17, 21 Luk.8:10, Act.7:25 28:26-27, Rom.15:21" (LXX), 2Co.10:12; with accusative of thing(s), Mat.13:23, 51, Luk.2:50 18:34 24:45; before ὅτι, Mat.16:12 17:13; before quæst. indir. Eph.5:17; ἐπὶ τ. ἄρτοις, Mrk.6:52; as subst. συνίων (ὁ σ. WH, mg.), a man of understanding, i.e. in moral and religious sense, Rom.3:11 (LXX).†

(AS)

to bring or set together; to perceive, understand; a man of understanding