abroad
在国外(副词,泛指在/到自己国家以外,不能修饰名词)
overseas
海外(副词/形容词均可,可修饰名词,比 abroad 更书面)
A growing number of students choose to study abroad as a way of broadening their cultural horizons and improving their language skills.
越来越多的学生选择出国留学,作为拓宽文化视野和提高语言技能的方式。
The company's overseas operations now account for more than sixty percent of its total annual revenue.
该公司的海外业务现在占其年度总收入的百分之六十以上。