The father of a family. In Roman law. The head or master of a family. This word is sometimes employed, in a wide sense, as equivalent to sui juris. A person sui juris is called ” paterfamilias ” even when under the age of puberty. In the narrower and more common use, a paterfamilias is any one invested with potestas over any person. It is thus as applicable to a grandfather as to a father. Ilunter, Rom. Law, 49.