Mum told me the facts of life when I was twelve.fact of lifeˌfact of ˈlife noun (plural facts of life) [countable] 
Mass unemployment seems to be a fact of life nowadays. Persuading others to accept the hard financial facts of life is not a very popular job.2the facts of life the details about sex and how babies are born: Mum told me the facts of life when I was twelve.
EXAMPLES FROM THE CORPUS
- Anyway, it's not neurotic, it's a fact of life, a biological, evolutionary thing.
- Despite the problems with groups they remain a major fact of life in all organizations.
- Financial insecurity has become a fact of life for significant segments of the middle and working classes.
- Homosexuality was not discussed, it was simply a fact of life.
- Incomplete systems are accepted as a fact of life.
- Leprosy was a disease, no more; it was an unpleasant fact of life, like poverty and illiteracy.
COLLOCATIONS FROM THE ENTRY Mum told me the facts of life when I was twelve.
1an unpleasant situation that exists and that must be accepted: Mum told me the facts of life when I was twelve. Mass unemployment seems to be a fact of life nowadays. Persuading others to accept the hard financial facts of life is not a very popular job.2the facts of life the details about sex and how babies are born: Mum told me the facts of life when I was twelve.