Translation guide
Japanese distinguishes between one's own mother-in-law and someone else's, and between formal and casual terms. The most common neutral term is 義理の母, but in daily speech, people use family terms like お義母さん or simply お母さん.
To talk about your own mother-in-law in a neutral or descriptive way, such as when introducing her or explaining the relationship.
Neutral, standard term for 'mother-in-law'. Literally 'mother by duty/relation'. Used in formal or descriptive contexts.
義理の母は料理が上手です。
My mother-in-law is a good cook.
More formal and written term for 'mother-in-law'. Can also mean 'stepmother', so context is important.
義母との関係は良好です。
My relationship with my mother-in-law is good.
To address your own mother-in-law directly or refer to her in casual family conversation.
The most common way to address your mother-in-law. Uses the same word as 'mother' (お母さん) but with the honorific prefix お and the kanji 義 (meaning 'in-law') optionally written. In speech, it sounds identical to 'mother'.
お義母さん、お茶をどうぞ。
Mother-in-law, please have some tea.
A slightly less formal version of お義母さん, dropping the honorific お. Still polite but more casual. Used by some families.
義母さん、今日は何時に帰りますか？
Mother-in-law, what time will you be back today?
Many Japanese people simply call their mother-in-law お母さん, the same as their own mother. This is very common and natural in daily life. The 'in-law' relationship is understood from context.
お母さん、これ美味しいですね。
Mom, this is delicious. (said to mother-in-law)
To talk about another person's mother-in-law politely.
Polite way to refer to someone else's mother-in-law. Uses お母様 (honorific for 'mother') with 義理の.
田中さんの義理のお母様にお会いしました。
I met Mr. Tanaka's mother-in-law.
Slightly less formal than お母様, but still polite. Commonly used in conversation.
彼の義理のお母さんはとても優しいそうです。
I hear his mother-in-law is very kind.
Used in legal documents, formal writing, or when specifying the legal relationship.
Literally 'spouse's mother'. Very formal and legalistic. Not used in daily conversation.
配偶者の母との同居を開始しました。
I began living with my spouse's mother.
It is extremely common for married people to call their mother-in-law お母さん (mom). This is not considered strange or disrespectful; it reflects the closeness of the family relationship. If you want to be explicitly clear, you can use お義母さん in writing, but in speech it sounds the same.
While 義母 (ぎぼ) is a correct term, it sounds stiff and formal. Using it in casual conversation about your own mother-in-law may sound distant or overly official. Stick to 義理の母 or お義母さん in most situations.