This is the 12710th most frequent Russian word.
костюмах
The Russian word "костюмах" means "costumes" or "suits" in the prepositional or plural instrumental case.
Here, 'костюмах' is used in the prepositional plural form to describe attire worn by the guests.
На празднике все гости были в красивых костюмах.
At the celebration, all the guests were dressed in beautiful costumes.
In this sentence, 'костюмах' refers to theatrical costumes of the actors, again in the plural prepositional case.
Актеры вышли на сцену в своих костюмах.
The actors came onto the stage in their costumes.
In this example, 'костюмах' is used to denote traditional attire, showing a variety of cultural expression, also in the plural prepositional case.