biological father; real father; natural father
Refers to one's biological father, as opposed to an adoptive, step, or foster father. Often used in formal or legal contexts, or when clarifying family relationships.
See also: 実母
He doesn't know his biological father's face.
戸籍には実父の名前が記載されている。
The biological father's name is recorded in the family register.
実父 is one's biological father, while 養父 is a father who raised the child through adoption or fostering rather than birth.
実父 means one's biological father, contrasting with 義父 which refers to a father-in-law, foster father, or stepfather who is not one's blood relation.
paternity test
Compound of 実 (jitsu, 'real; true') and 父 (fu, 'father'). The reading じっぷ is a regular sound change from じつふ.