べきだ

The grammar structure べきだ expresses a strong sense of obligation, duty, or moral recommendation – "should do" or "ought to do." It is used when the speaker believes something is the right or proper course of action, often based on social norms, common sense, or ethical judgment.

Basic usage

Attach べきだ to the dictionary form of a verb. It carries a stronger tone than 〜～ほうがいい, implying moral or logical obligation rather than casual advice.

する → すべき / するべき

The verb する has two accepted forms: すべきだ (traditional/literary) and するべきだ (common in modern speech). Both are correct.

Negative: べきではない

To express "should not," use べきではない (or the polite べきではありません). The negative is attached to だ, not to the verb itself.

Past: べきだった

To express regret about something that should have been done – "should have" – use べきだった.

Nuances and comparison with ～ほうがいい

While 〜～ほうがいい offers friendly, personal advice ("it would be better to…"), べきだ conveys a stronger sense of what is right or expected. It can sound preachy or authoritative if directed at someone, so it is used for general statements or self-reflection rather than direct commands to others.

In polite speech, べきです is used.