- used for emphasis to refer two people or things, regarded and identified together双方, 两者：
as predeterminer both his parents indulged him父母都很娇惯他
I urge you to read both these books
我劝你这两本书都要读一下
as determiner she held on with both hands她用双手拿着
he was blind in both eyes
他双目失明
as pronoun a picture of both of us together我俩的合影
Jackie and I are both self-employed
杰基和我都自己当老板
he looked at them both.
他看着她俩。
- used before the first of two alternatives to emphasize that the statement being made applies to each (the other alternative being introduced by 'and'.)［用在两个选项中的第一个之前, 表示所作的阐述对这两个选项都适用, 另外一个选项前用的是'and'］ …和…（两者）都, 不仅…而且, 既…又：
it has won favour with both young and old
这既受到了年轻人的欢迎也受到了老年人的欢迎
studies of zebra finches, both in the wild and in captivity.
对金翅雀的研究, 既有野生的, 也有家养的。
USAGE
When both is used in constructions with and, the structures following 'both' and 'and' should be symmetrical in well-formed English. Thus, studies of zebra finches, both in the wild and in captivity is better than, for example, studies of zebra finches, both in the wild and captivity. In the second example, the symmetry of in the wild' and in captivity' has been lost. Other examples: her article is detrimental both to understanding and to peace （not her article is detrimental to both understanding and to peace）.
短语
have it both ways
- benefit from two incompatible ways of thinking or behaving二者兼得：
countries cannot have it both ways: the cost of a cleaner environment may sometimes be fewer jobs.
国家难以二者兼得, 因为环境更清洁的代价有时意味着减少工作机会。
词源
Middle English: from Old Norse báthir.