the soft part of a bed, that you lie on 床垫 
a soft/hard mattress 软／硬床垫 We can sleep on a mattress on the floor. 我们可以睡在地板上的床垫上。 an old bed with a lumpy mattress 床垫高低不平的旧床
Oxford Collocations Dictionaryadjective- double
- king-size
- queen-size
- …
- on a/the mattress
- under a/the mattress
Word OriginMiddle English: via Old French and Italian from Arabic maṭraḥ ‘carpet or cushion’, from ṭaraḥa ‘to throw’.
