In the survey, over 30% of adults aged 30-35 described themselves as unmarried.

unmarried 是由前缀 un-（表示"否定"）和形容词 married（已婚的）组成的复合词。un- 加在形容词前通常表示"不、非"的意思，所以 unmarried 意思是"未婚的"。