～ことだ

About

The ～ことだ pattern is used at the end of a sentence to give firm suggestions/advice. Usually, ～ことだ statements indicate that the speaker has a high degree of confidence in the suggestion/advice they are giving.

～ことだ can follow casual form verbs in either the negative or affirmative.

E.g. お金かねが欲ほしいなら、ちゃんと仕事しごとを探さがすことだ。 "If you want money you need to find a job."

E.g. 高木たかぎ先生せんせいの授業中じゅぎょうちゅうには話はなさないことだよ。 "No talking during Mr. Takagi's class."

～ことだ's strong tone can be softened with the addition of the よ or ね particles.

Summary

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  ～ことだ is used to give firm suggestions and advice

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  ～ことだ follows casual form verbs