v. if two things alternate or you alternate them, they change from one to the other in a repeated pattern (使)轮流;(使)交替 a. happening on one day, week, etc. but not on the day, week, etc. that immediately follows 间隔的 n. [C] (mainly AmE) a person or thing that replaces another, and can act or be used instead of them 替换(人)物