Translation guide
How to express that someone cannot do something, or lacks the ability to do something, in natural Japanese.
Expressing that someone cannot do something, or something is impossible.
The standard way to say 'cannot do V'. Polite form is ことができません.
I cannot swim.
He cannot come.
The potential negative form of verbs is very common in casual speech. For ru-verbs, replace る with られない; for u-verbs, change the ending to the え-row + ない.
A noun or na-adjective meaning 'impossible'. Often used in formal or written contexts.
That plan is impossible.
Expressing that someone is not good at something, or lacks the ability due to insufficient skill.
Means 'to be bad at N'. N is a noun or nominalized verb (こと).
I am bad at singing.
Used with a verb to say 'bad at doing V'.
He is bad at cooking.
Means 'weak point' or 'not good at'. Softer than 下手, often implies a personal feeling of inadequacy.
Expressing that something cannot be done due to external circumstances, rules, or physical constraints.
Means 'must not do V' or 'it is not allowed to do V'. Used for prohibitions.
You must not take photos here.
Expresses that one cannot do something due to social or moral obligations, not just ability.
I cannot break my promise.
Expressing that one cannot do something because they lack the necessary tools, money, time, etc.
The same pattern as general inability, but often accompanied by a reason.
I can't buy it because I have no money.
Casual way with potential negative form, often followed by から or ので.
I can't go because I have no time.
Both mean 'cannot', but できない is more formal and explicit, while the potential negative form (e.g., 食べられない) is more common in casual speech. Use できない in writing or formal situations.
I can't eat natto.
I cannot eat natto. (polite)
The English noun 'inability' is often best expressed with verb phrases in Japanese. Using a direct noun like 不能 (ふのう) is very formal and limited to specific contexts (e.g., 機能不全). Avoid translating 'inability' as a standalone noun.
I'm not good at math.