Translation guide
Describes someone who is slow to understand, not sharp, or lacking intelligence. Japanese has several common words and phrases to express this, ranging from blunt to softer, indirect expressions.
To describe a person who takes time to grasp things or is generally not bright.
Common word meaning 'slow', 'dull', or 'obtuse'. Can refer to physical slowness or mental dullness.
He is slow on the uptake.
Means 'stupid', 'idiotic', or 'dull-witted'. More insulting than 鈍い. Often used for someone who makes foolish mistakes.
How could you make such a dumb mistake?
Formal/literary term meaning 'stupid' or 'dull-witted'. Stronger and more serious than 鈍い.
He is a dull-witted man.
To bluntly say someone is not smart, often in a derogatory way.
The most common word for 'stupid' or 'fool'. Can be used playfully or seriously. Very versatile.
He is really stupid.
Kansai dialect equivalent of 馬鹿, but widely understood. Often used jokingly.
Means 'low intelligence' or 'feeble-minded'. Harsh and clinical, often used as an insult.
To emphasize that someone is stubbornly slow to understand or insensitive.
Literally 'head is hard'. Means inflexible thinking, stubborn, or slow to accept new ideas. Not necessarily low intelligence, but rigid.
He's so thick-headed, you can't reason with him.
Means 'slow to understand' or 'obtuse'. More about comprehension than stubbornness.
He is a slow-witted student.
Means 'insensitive' or 'thick-skinned'. Often used for emotional dullness, but can imply mental slowness.
To refer to intellectual disability or severe slowness, often in clinical or euphemistic contexts.
Standard term for 'intellectual disability'. Neutral and appropriate in formal contexts.
He has an intellectual disability.
Short for 精神遅滞 (intellectual disability), but can be used alone to mean 'retardation'. Often considered outdated or offensive; use with caution.
Can be offensive if used casually. Prefer 知的障害 in formal settings.
Means 'slowpoke' or 'dimwit'. Very casual and derogatory. Not clinical.
English 'dull-witted' does not have a single perfect equivalent. Using 鈍い alone may be too vague; often you need a phrase like 頭の回転が鈍い to clarify mental slowness.
馬鹿 is standard Japanese, while 阿呆 is Kansai dialect. Both mean 'stupid', but 阿呆 can sound softer or more playful depending on region. In Kanto, 馬鹿 is more common; in Kansai, 阿呆 is preferred.
Don't say stupid things.
低能な奴だ。
What a dimwit.
彼は鈍感で、人の気持ちがわからない。
He is so dense, he doesn't understand people's feelings.
彼は精神の発達に遅れがある。
He has a developmental delay.
What a slowpoke.