The term "natural fathers" is often used to refer to a biological father, meaning the man who impregnated the mother of the child. However, there are several synonyms for this term that can be used in different contexts. Some of these synonyms include birth fathers, genetic fathers, biological fathers, sire, and sperm donor. Each of these terms has a slightly different connotation and may be used in specific situations. For example, "sperm donor" is a more clinical term used when someone donates sperm for the purpose of artificial insemination. Overall, these synonyms can add clarity and nuance to discussions about fathers and their roles in the family.