Lifetime is a term that refers to the length of a person's life or the duration of a particular thing. However, there are many synonyms for the word lifetime that can be used interchangeably in different contexts. These include terms like duration, span, existence, life span, life cycle, tenure, era and generation. These words hold different meanings but are often used to refer to a certain period of time or lifespan. Whether it's discussing the duration of a project, the length of a person's existence or the era in which someone lived, these alternatives to lifetime can help you communicate more effectively.