1. lawsuit - this is used for a civil law case. I don't hear it used for criminal cases, though I'm not a lawyer.
2. trial - this is what a court does when someone's innocence or guilt is questioned. If you are charged with a crime, you will be put on trial.
3. sue - this is taking someone to court to obtain compensation for a wrong, which could be physical, economic or social.
Hope That Helps
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