* Mom (mother)
* Dad (father)
However, there are many other ways to refer to parents, depending on context and culture:
Formal:
* Mother
* Father
* Parents
* Mum (British English)
* Dad (British English)
Informal:
* Mama
* Papa
* Mommy
* Daddy
* Mummy
* Pops
* Ma
* Pa
* Mother/Father figure
* Guardian
Other terms:
* Stepmother/Stepfather
* Adoptive parents
* Foster parents
* Grandparents (when referring to parents of your parents)
The best way to refer to someone's parents depends on the specific situation and your relationship with them.