mother church; main church
In Christian contexts, refers to a principal church that oversees or gives rise to other churches, such as a cathedral or founding congregation.
The mother church of this region supports many smaller churches.
church where one was baptized
Specifically the church where a person received baptism; often has personal or spiritual significance.
彼は洗礼を受けた母教会を訪ねた。
He visited the mother church where he was baptized.