What do you understand by the term 'Cause of Action'. Why is this most important part of plaint ?

The term 'Cause of Action' refers to a set of facts or allegations that make up the grounds for filing a lawsuit. A Cause of Action is therefore by its very nature essential to a Suit, since without a Cause of Action a Civil Suit cannot arise. 'The Cause of Action' is that part of the Plaint which explains the background upon which the differences and disputes arose between the plaintiff and the defendant. In fact, the part of the plaint is the most important part, which explains the basis of the fight between the plaintiff and the defendant. Further this will reveal the agreement, relationship between them, when the breach started, where is happened and whether the suit is filed within the limitation period etc. To win a case the Plaintiff must prove the major legal points of the case lie in his favour; these are called the 'elements' of that cause of action. For example, for a claim of negligence, the elements are: the (existence of a) duty, breach (of that duty), proximate cause (by that breach), and damages. If a plaint does not allege facts sufficient to support every element of a claim, the court, upon motion by the opposing party, may dismiss the plaint for failure to state a claim for which relief can be granted. The defendant to the Cause of Action must file a Written Statement to the plaint in which, he may admit or deny the claims made by the plaintiff and give his proof for the same and his written arguments to show how the law supports him. The Written Statement may also contain counterclaims in which the states its own causes of action. Finally, the answer may contain affirmative defences. Almost all defences must be raised at the first possible opportunity either in the Written Statement or by motion, else they are deemed waived by the Court.