ことだ | Grammar

Structure

[verb (dictionary form)] + ことだ [verb ない-form] + ことだ

Description

ことだ gives advice: "you should", "the thing to do is". It follows a verb in the dictionary form, or the ない-form for advice not to do something.

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If you want to stay healthy, you should exercise every day.

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If you want to succeed, you should work hard.

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You shouldn't stay up late at night.

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You shouldn't speak ill of others.

The advice comes from someone who knows better – a parent, a teacher, a doctor – and sounds like a rule of thumb. Said to a boss or a teacher, it is rude. The first half often sets up the goal with きごう〜たければ, きごう〜たいなら or きごう〜ためには. The polite form is ことです.

The verb stays in the dictionary form or the ない-form. A た-form turns the sentence into something else: ×行ったことだ.

ことだ or ほうがいい

is advice for this person in this situation, and it often takes the た-form. ことだ states a general principle that would hold for anyone in the same place, so it can sound like a lecture.

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If you have a fever, you'd better go home early.

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When you catch a cold, you should rest well.

After an adjective, ことだ is a different pattern: an exclamation, as in なん何とうれしいことだ, "how happy that makes me".

Examples

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If you want to get good at Japanese, you should practice every day.

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If you want to pass the exam, you should study more.

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When you catch a cold, you should rest well.

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You shouldn't compare yourself to others.

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If you don't understand, you should ask the teacher.

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You should gain various experiences while you're young.

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For your health, you shouldn't eat too many sweets.

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If you want to be trusted, you shouldn't tell lies.

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First, you should think for yourself.

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If something happens, you should consult someone right away.

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Even if you're busy, you shouldn't cut down on sleep.

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You should listen carefully to what others say.

References

ことだBunpro