This is the 14044th most frequent Korean word.
매트리스
Mattress.
In this sentence, '매트리스' is used as the subject being the object purchased.
새 매트리스를 구입했어요.
I bought a new mattress.
Here, '매트리스' is describing the object that has the attribute of being hard.
매트리스가 너무 딱딱해서 불편해요.
The mattress is too hard, so it's uncomfortable.
In this usage, '매트리스' refers to the object that was swapped in term of location.