custom vs. costume
custom
(something that people in a particular society, place, or time do because it is traditional)
- We are new here and unfamiliar with the local customs.
- The custom of pinning money to the bride’s dress is becoming less common here.
costume
(a set of clothes that are typical of a particular country or time in the past)
- The national costume of Japan shows his nationality.
- Some of the singers were wearing historical costumes.