1. （生物的）生活史，生活周期
The life cycle of an animal or plant is the series of changes and developments that it passes through from the beginning of its life until its death.

2. （想法、产品、组织等的）存在周期
The life cycle of something such as an idea, product, or organization is the series of developments that take place in it from its beginning until the end of its usefulness.

1. a series of stages through which an organism passes between recurrences of a primary stage

2. the course of developmental changes in an organism from fertilized zygote to maturity when another zygote can be produced