-고 나다: After Finishing — Completion Is the Point

-고 나다 (most often -고 나서 in instructions) means after finishing A — the finishing is not background noise.

Gloss: after finishing — the completion is the point. 우리말샘 auxiliary 나다 in -고 나다: the front action has ended.

What it does — done, then next

-은 다음에 can say after without spotlighting completion. -고 나서 says: A is complete; now B.

씻고 나서 요리해요.
고기를 양념에 넣고 나서 기다려요.
일하고 나면 피곤해요.
영화를 보고 나서 이야기해요.

Cooking and lab-style steps need this honesty:

썰고 나서 볶아요.
불을 끄고 나서 뚜껑을 덮어요.

Do the first thing fully. Then the second.

고 나다 vs 고 나서

-고 나다 is the auxiliary frame. -고 나서 is the everyday sequencing shape (-고 나- + -아서). Courses and recipes lean on -고 나서 because the next step wants a connective hinge. Same completion family — do not treat them as unrelated words.

먹고 나면 졸려요.          after eating (as a finished event), sleepy
먹고 나서 설거지해요.      after finishing eating, wash up

Versus softer after / and

넣은 다음에 기다려요.     plain after
넣고 나서 기다려요.       finishing the putting-in matters
넣고 기다려요.           looser and

When to use — and when plain after is enough

Use -고 나서 when skipping completion would break the procedure (heat off before lid; marinade in before wait).

Use -은 다음에 when you only need schedule order (after class, meet).

Keep it on verbs — dictionary attachment is actional, not adjectival states.

Practice rule: if a careful listener should hear “don’t start B until A is done,” choose -고 나다/나서.