The Greek noun gelos (γέλως) means laughter. Appearing only once in the New Testament (James 4:9), it stands in sharp contrast to the joy and laughter promised in the Beatitudes. James calls for the laughter of frivolous worldliness to be turned to mourning — not because laughter is evil, but because misplaced laughter in the face of sin reveals spiritual blindness.
James's use of gelos — 'Let your laughter be turned to mourning' — is a call to genuine contrition. There is a laughter that comes from righteous joy in God (Psalm 126:2) and a laughter that comes from spiritual complacency. The New Testament holds both in tension: James calls the self-satisfied to weep, while Luke promises that those who weep will laugh. True joy, Scripture teaches, passes through the valley of honest repentance before arriving at lasting celebration.