Duhaime's Law Dictionary

Agnatio Definition:

Latin: members of a group having a common male ancestor.

Related Terms: Cognates

Relationship on the paternal (father's) side.

Sometimes anglicized as agnates.

Also agnation; members of the group being called agnati.

Membership to an agnatio depended on a direct blood link to the elder male except that marriage and adoption were two other methods of gaining entrance to an agnatio.

A principle of early Roman law that organized estates based on the father's lineage. Even a wife who entered a family took on the legal status as no more than a sister to her own children in the eyes of the law (see Blackstone's desciption of this in the Legal Definition of Cognates).

Distinguished from cognates which is that group of persons who are linked by relations on the mother's side.


  • Burrill, A., Law Dictionary and Glossary, Vol. I (New York: Baker, Voorhis & Co., Law Publishers, 1867), page 74
  • Howe, W., Studies in the Civil Law (Littleton, Colorado: Fred B. Rothman & Co., 1980)

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