Translation guide
In Japanese, the word for 'grandchild' is 孫 (まご). Unlike English, Japanese does not distinguish between grandson and granddaughter in the basic term. Gender can be specified by adding 息子 (むすこ) for 'son' or 娘 (むすめ) for 'daughter' after 孫, but this is not always necessary. When referring to one's own grandchild, no honorific is used. When referring to someone else's grandchild, the honorific prefix お or 様 (さま) is added.
The most common and neutral way to refer to a grandchild, without specifying gender.
The standard word for 'grandchild'. Used for both grandson and granddaughter. When talking about your own grandchild, use it without honorifics. When talking about someone else's grandchild, add お or 様 for politeness.
私の孫は今年5歳になります。
My grandchild will be five years old this year.
お孫さんはおいくつですか？
How old is your grandchild?
Specifically referring to a male grandchild.
Literally 'grandchild son'. Used to explicitly refer to a grandson. Less common than just 孫, but used when gender clarification is needed.
孫息子が大学に入学しました。
My grandson entered university.
Means 'male grandchild'. A descriptive way to specify grandson.
男の孫が二人います。
I have two grandsons.
Specifically referring to a female grandchild.
Literally 'grandchild daughter'. Used to explicitly refer to a granddaughter.
孫娘はピアノが上手です。
My granddaughter is good at piano.
Means 'female grandchild'. A descriptive way to specify granddaughter.
女の孫が生まれました。
A granddaughter was born.
Politely referring to another person's grandchild.
Polite form with honorific prefix お and suffix さん. Used when speaking about someone else's grandchild. Very common in conversation.
お孫さんはとてもかわいいですね。
Your grandchild is very cute.
More formal version using 様 (さま). Used in very polite or formal situations, such as business or formal letters.
お孫様のご入学おめでとうございます。
Congratulations on your grandchild's entering school.
Japanese nouns do not change for plural. 孫 can mean one grandchild or multiple grandchildren depending on context. To specify number, use counters like 一人 (ひとり) for one person, 二人 (ふたり) for two, etc.
While 孫息子 and 孫娘 exist, they are not as commonly used as simply 孫. In many contexts, gender is understood from context or names, so specifying gender may sound unnatural unless necessary.