expression, noun
master of the household; head of the family
A somewhat formal or literary term for the person who leads a household, often implying authority and responsibility. Not used for modern casual 'head of the family' in everyday conversation.
彼は一家の主として、家族を支えてきた。
As the master of the household, he has supported his family.
家長 is a more common and neutral word for 'head of the family', whereas 一家の主 carries a slightly more formal or old-fashioned nuance.
Compound of 一家 (one family/household) + の (possessive particle) + 主 (master/head). The reading あるじ for 主 is an older native Japanese word for 'master' or 'owner'.