In the United States, in order for a person to sue, you must be of legal age (18, or an emancipated minor), legally competent, and have what is referred to as "standing".
Standing means that:
- You were the party which suffered some form of damage, OR, you are the legal guardian/executor/ etc. of a person which cannot themselves sue (being a minor, mentally incompetent, dead, etc.) but which suffered damage
- The damage sustained must be actual or imminent, not theoretical or hypothesized. That is, you cannot sue because something might possibly cause you damage. You must actually suffer damage or the damage must have a very significant possibility of occurring in the very near future. The later case ("very significant possibility") has a strict legal definition, not the common language use.
- The damage you receive must be reasonably attributed to the defendant, not some third party (in practice, this is often abused when filing a lawsuit, but is generally quickly resolved when the case actually begins).
- The damage you sustain must be able to be stopped (or mitigated) by a favorable decision in the lawsuit. That is, if the damage you receive cannot be fixed (including via monetary compensation) or is inevitable, then you cannot bring the suit.
A person may sue any legal entity. However, certain suits against various government entities are disallowed, under the concept of Sovereign Immunity.
