A foundational wisdom verb meaning to perceive with insight, to distinguish between things, to give careful attention to. More than mere knowing (yada), biyn involves thoughtful analysis and discrimination — the heart's ability to weigh what it observes.
Biyn is the great Proverbs verb for wisdom-formation. Proverbs constantly calls the young man to 'get understanding' as a life goal second only to fearing God. The noun binah (H998) is understanding personified. In Isaiah, the failure of Israel is precisely their inability to biyn — to perceive what God is doing.