おじいさん・お祖父さん・お爺さんojiisan[2]nakadaka (mid-high)

1. noungrandfatherusu. お祖父さん when written with kanji
   おじいさんは少すこし耳みみが遠とおいんだ。↗

   My grandfather is a bit hard of hearing.
2. nounmale senior-citizen; old manusu. お爺さん when written with kanji
   おじいさんはその木きの人形にんぎょうをピノキオと名なづけました。↗

   The old man named the wooden doll Pinocchio.

• SynonymじいさんCasualMore casual than 「お祖父さん」: used for a grandfather within the family or for old men in general, and it can sound slightly disrespectful.
• Synonym祖父そふWrittenThe written, formal term for your own grandfather when speaking to others, as in 「祖父は九十歳です」; it is not used to address him directly.
• SynonymじじCasualSlang for an old man, often with contempt, as in 「くそじじい」; in families it can also serve as an affectionate name for one's grandfather.
• SynonymおじいちゃんCasualAn affectionate form, the usual way for children to call their grandfather; also used of elderly men in general.
• Related翁おきなWrittenAn archaic, literary word for an old man, met mainly in folk tales and Noh, as in 「竹取の翁」.
• RelatedおじいさまFormalMore respectful than 「お祖父さん」; used mostly for another person's grandfather or in refined, upper-class families.
• Related老翁ろうおうWrittenA written/formal word for an aged man, found mostly in literary description; not used to address family members.
• Related老夫ろうふWrittenA rare, archaic written term for an elderly man; in everyday speech people say 「お爺さん」.
• Related老爺ろうやWrittenA written word for an old man, now mostly literary and little used; everyday speech prefers 「お爺さん」.
• AntonymおばあさんNeutralThe female counterpart of 「お祖父さん」, meaning grandmother; for elderly women in general it is usually written 「お婆さん」.

Call your own grandfather 「お祖父さん」 by default, and write 「お爺さん」 for an old man in general. Children say 「お爺ちゃん」, mention your grandfather to others as 「祖父」, and use 「おじい様」 for extra respect. The remaining words are literary or slang terms for old men; 「お祖母さん」 is the female counterpart.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 祖父そふ。父方ちちかた、母方ははかたを区別くべつしない。
2. 祖父そふに限かぎらず、祖先そせんのうちの男性だんせい。
3. 高齢こうれいの男性だんせい。