【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.