A fact of life = Any aspect of human existence that must be acknowledged, or regarded as unalterable (usually not pleasant)
- Old age is a fact of life.
- Stress is a fact of life from time to time for all of us.
- We should understand that death is a fact of life.
The facts of life = The facts concerning sex, reproduction, and birth (teaching of the same, exp., to a child)
- Some people feel that the facts of life should be taught in school.
- Raju learned the facts of life from his classmates.
‘The birds and the bees‘ is a euphemism(a mild or indirect word or expression) for ‘the facts of life’.
- It’s time Father told the children about the birds and the bees.
- She is so ignorant. She probably has not been taught so much as the birds and the bees.