noun
ancestor; forefather; progenitor
Formal or concise noun for an ancestor at the beginning of a lineage, family, people, or tradition; common in the pattern Xの祖.
この一族の祖は、江戸時代にこの村へ移り住んだと伝えられている。
It is said that the ancestor of this family moved to this village in the Edo period.
その人物は後に王家の祖となった。
That person later became the progenitor of the royal family.
noun
founder; originator; pioneer; inventor
Used honorifically or historically for the person regarded as the beginning of a school, field, invention, or movement; often translated according to context as founder, originator, or pioneer.
彼は日本の近代医学の祖と呼ばれている。
He is called the father of modern medicine in Japan.
この発明家はロボット工学の祖の一人とされる。
This inventor is regarded as one of the pioneers of robotics.
noun
Original or old meaning. In modern Japanese, 祖父 is the normal word for grandfather; standalone 祖 in this sense is mainly historical or explanatory.
古い用法の「祖」は、祖父、つまり祖父親を指すことがある。
In old usage, 祖 can refer to a grandfather.