How to Say "Grandpa" in Japanese

お爺ちゃん

ojii-chan[o̞ʑiːt͡ɕã̠ɴ]

In Japanese, the English word "grandpa" can be expressed as お爺ちゃん (ojii-chan). Wiktionary also lists お爺さん (ojii-san).

Meaning: grandfather (informal) (noun)

Ways to say it

“grandpa” in Japanese
Japanese	Romanization (Wiktionary)	IPA
お爺ちゃん	ojii-chan	[o̞ʑiːt͡ɕã̠ɴ] (narrow)
お爺さん	ojii-san	[o̞ʑiːsã̠ɴ] (narrow)

お爺ちゃん is an affectionate, informal way to say grandpa, often used by children or within a family.

ojii-chan

The word お爺さん is often used as a polite way to address any elderly man on the street, even if he is a complete stranger.
In some regions of Japan, specific variations of the word for 'grandpa' are used to distinguish between the grandfather on your mother's side and the one on your father's side.
The word 'grandpa' in Japanese is often replaced by the much more formal 祖父 (sofu) when speaking to outsiders about your own grandfather.

お爺さんは独りで暮らしています。
Grandpa lives alone.
This sentence illustrates the use of お爺さん.
Tatoeba #11782693 by bunbuku, translation #12370649 by CK
私たちはお爺ちゃんとお婆ちゃんが心配だ。
We're worried about Grandma and Grandpa.
This sentence shows how to use お爺ちゃん.
Tatoeba #993812 by mookeee, translation #247158 by CK
あなたのお爺さんはどこに住んでいますか。
Where does your grandpa live?
This sentence demonstrates how to use お爺さん.
Tatoeba #2876228 by chaDQI, translation #394891 by Dorenda
Okaasan no jiichan wa eigo ga jyozu desu ne. (お母さんのじいちゃんは英語が上手ですね。)
Your mom's grandpa is good at English, isn't he?
Watashi no jii wa ikemen desu yo! (私のじいはイケメンですよ！)
My grandpa is a handsome guy!
1 more sentence on Tatoeba

Two siblings are talking about their grandfather's upcoming visit.

美咲 Misaki

お爺ちゃんはいつ来るの？
ojiichan wa itsu kuru no?
When is grandpa coming?
大翔 Hiroto

来週の土曜日だよ。
raishuu no doyoubi da yo.
It is next Saturday.
美咲 Misaki

お爺ちゃんにプレゼントを渡したいな。
ojiichan ni purezento o watashitai na.
I want to give grandpa a present.
大翔 Hiroto

僕も何か用意するよ。
boku mo nanika youi suru yo.
I will prepare something too.

Sources

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