To judge, to decide, to evaluate, to condemn. Krinō covers the whole range of judgment: forming opinions, making legal decisions, rendering verdicts, and the final divine judgment. It gives us 'crisis' (a decisive moment) and 'criterion' (a standard of judgment).
Jesus said, 'Do not judge, so that you may not be judged' (Matthew 7:1), yet also 'judge with right judgment' (John 7:24). The prohibition is against self-righteous condemnation; the command is for discerning evaluation. God's final judgment is perfectly just — He judges not by appearance but by truth (Romans 2:2). Christ was given all judgment by the Father (John 5:22), and will judge the living and the dead.