1.
grandfather
The father of one's parent.
祖父 is the formal term for one's own grandfather, used in polite or written contexts.
FORMALITY LEVELS:
DISTINGUISHING GRANDFATHERS:
RELATED FAMILY TERMS:
USAGE NOTE:
Use 祖父 when speaking about your grandfather to others in formal situations. Use おじいちゃん when speaking directly to him or in casual contexts.