Children often seek constant reassurance from their parents about their safety.

reassurance 是由前缀 re-（表示"再次"）和 assurance（保证）组成的复合名词。assurance 本身来自动词 assure（保证、使确信），加上名词后缀 -ance 构成。reassurance 的字面意思是"再次保证"，指为了消除不安或疑虑而给予的安慰和确认。