～べきだ

• Reading: べきだ
• Romaji: beki da
• Formation: Verb dictionary form + べきだ (する → するべき / すべき)

Meaning

An auxiliary expression meaning 'should' or 'ought to,' used to express the speaker's judgment or moral obligation that something is the right course of action.

べきだ conveys the speaker's strong belief that a particular action is the proper, expected, or morally correct thing to do. It is stronger than ほうがいい, which merely suggests a preferable option, and carries a tone of moral or logical obligation. The negative form べきではない means 'should not.' べきだ is typically used for general principles or advice directed at others, and can sound preachy if overused in casual settings. It attaches to the dictionary form of verbs, with the notable exception of する, which can become either するべき or すべき.

Examples

1. 学生は毎日復習するべきだ。 Students should review every day.
2. 約束は守るべきだと思います。 I think promises should be kept.
3. 親として子どもの話を聞くべきだ。 As a parent, you should listen to your children.

Usage Guide

Context: spoken, written, everyday

Tone: advisory

Do Say

• 健康のために野菜をもっと食べるべきだ。
• 大切なことは直接会って話すべきです。
• この問題は早めに解決すべきだと思う。

Don't Say

• 学生は毎日復習するべきではない。(Using the negative form when intending the affirmative — べきではない means 'should not') → 学生は毎日復習するべきだ。
• 明日雨が降るべきだ。(Using べきだ for weather predictions — べきだ expresses obligation, not natural phenomena) → 明日雨が降るだろう。

Origin & History

Derived from the classical Japanese auxiliary verb べし, which expressed obligation, conjecture, and inevitability. In modern Japanese, べきだ retains primarily the obligation sense.

Cultural Context

Generation: All ages

Social background: Universal