On Jeopardy just now the question asked for the Latin term meaning "father of the family". Contestant Tricia correctly answered "paterfamilias". This is an interesting term - if you've ever studied Latin you may notice that it looks wrong. The citation form of "family" is familia, and as a first declension noun, its genitive singular should be familiae, just as "the girl's father" is pater puellae. So why is "father of the family" not paterfamiliae?
The answer is that in ordinary Latin the genitive singular of familia is indeed familiae. paterfamilias is a fixed expression not only in English but in Latin itself. It is a legal term, designating the legal head of the household. In Roman Law the paterfamilias had enormous power over his household. In theory he had power of life and death not only over his slaves but over his children, and he was legally responsible for the actions of members of his household. A slave might be a father and have a family, but that did not make him paterfamilias.
The reason for the peculiar genitive singular is that as a legal term it was carried down unchanged from Archaic Latin, a language different in significant respects from the Classical Latin that one usually learns. One of the innovations of Latin with respect to Proto-Indo-European is the development of a nominal declension based upon that of the pronouns. familias is the form that we would expect, with genitive singular suffix /s/. The regular form familiae reflects the innovation by which the genitive singular suffix /s/ was replaced by /i/ (with /a/ + /i/ spelled <ae> in Latin).
Posted by Bill Poser at April 18, 2007 12:11 AM