在英语中，buy 后面通常加可数名词单数。例如:
I buy apples every week. (我每周买苹果。)
She buys a new dress every year. (她每年买一条新裙子。)
但是，如果可数名词是复数形式，buy 后面也会加上复数形式。例如:
They buy many books. (他们买许多书。)
She buys two pairs of shoes. (她买两双鞋。)
不可数名词通常不能与 buy 连用，因为不可数名词没有单复数形式。例如:
I buy milk. (我买牛奶。)
She buys a book. (她买一本书。)