계단

In a sentence

• 계단을 조심히 내려가세요.

  Please walk down the stairs carefully.

  Here, '계단' is used to refer to the physical stairs one is walking down.

• 저 건물의 계단은 매우 높아요.

  The stairs in that building are very steep.

  In this sentence, '계단' describes the steepness of a specific set of stairs as a feature.

• 그는 계단에서 미끄러져 넘어졌어요.

  He slipped and fell on the stairs.

  Here, '계단' serves as the location where the action occurred.