Translation guide
The concept of a person's mental ability expressed as the age at which an average person reaches that same ability. In Japanese, this is typically expressed using the term 精神年齢 (seishin nenrei), but the concept can also be conveyed through descriptions of maturity or childishness.
The standard psychological concept of mental age, often used in testing or clinical contexts.
Describing someone's behavior or personality as being like a certain age, often implying immaturity or precociousness.
Literally 'mental age is low', used to say someone is immature or childish.
彼は大人なのに精神年齢が低い。
He's an adult but has a low mental age.
精神年齢 (mental age) is often contrasted with 実年齢 (actual/chronological age) or 肉体年齢 (physical age). In casual conversation, 精神年齢 is the go-to term for discussing maturity levels.
精神年齢と実年齢のギャップが大きい。
There's a big gap between mental age and actual age.
While 精神年齢 is understood, in very casual conversation, phrases like 中身は子供 or 大人げない may sound more natural than directly saying 精神年齢が低い. Use 精神年齢 when you want to be precise or slightly analytical.
The direct translation and standard term for 'mental age' in psychology and education.
彼の精神年齢は10歳と判定された。
His mental age was assessed as 10 years old.
A less common synonym for mental age, literally 'intelligence age'. Used in some psychological contexts.
知能年齢は実年齢と必ずしも一致しない。
Mental age does not necessarily match chronological age.
Literally 'mental age is high', used to say someone is mature for their age.
彼女はまだ若いけど精神年齢が高い。
She's still young but has a high mental age.
Pattern to specify a mental age, e.g., 精神年齢が5歳 (mental age of 5).
あの人の精神年齢は小学生レベルだ。
That person's mental age is at an elementary school level.
Literally 'inside is a child', a common way to say someone is childish despite their age.
彼は体は大きいけど中身は子供だ。
He's big in body but a child inside.
Means 'immature' or 'childish' for an adult. Implies low mental age.
そんなことで怒るなんて大人げない。
Getting angry over something like that is so immature.