Suit, lawsuit, action, cause, case are all used to designate legal proceedings instituted for the sake of demanding justice or enforcing a right.
Though often used interchangeably in the sense of lawsuit , they may have certain differences in their connotations and their applications. Suit stresses the attempt of a complainant through litigation to gain an end (as redress for a wrong, recognition of a claim, or the enforcement of law); it therefore may be used of the proceedings from the time of formal application through the prosecution.
Lawsuit can add to suit the implication of actual trial in court and often that of judicial decision; it may therefore refer to the entire proceedings.
Action comes very close to suit , but it is relatively colorless and throws the emphasis on actual proceedings rather than on petition. In technical legal use, however, it is a proceeding in a court of law which is distinguished from a suit in equity and which has for its end the ascertainment of facts. If the complainant’s position is found correct in such an action, an appropriate legal remedy may then be applied.
Cause emphasizes the grounds on which one institutes a suit; consequently, like suit , it implies the plaintiffs point of view, but it suggests even more strongly his sense of the justice of his demand.
Case, like cause , may imply rather the grounds of action than the actual proceedings but, unlike cause , may view or present these grounds from either or both points of view.
However case often is applied to the entire proceedings in a lawsuit including the judicial decision.