Formal:
* Parents: This is the most common and neutral term.
* Mother and father: This is a more specific and formal way to refer to them individually.
Informal:
* Mom and Dad: This is a common and affectionate way to refer to them.
* Mummy and Daddy: This is a childlike term used for parents.
* Your folks: This is a casual way to refer to parents, especially in a conversation with someone who knows them.
Other:
* Biological parents: This term is used to emphasize that they are the biological parents of a child.
* Legal guardians: This term is used if the parents are not the biological parents but have legal custody of the child.
The best way to refer to a mother and father depends on the situation and the relationship you have with them.