That which is important; that which is not merely of form but of substance. 2. When a bill for discovery has been filed, for example, the defendant must answer every material fact which is charged in the bill, and the test in these cases seems to be that when, if the defendant should answer in the affirmative, his answer would be of use to the plaintiff, the answer would be material, and it must be made. 3. In order to convict a witness of a perjury, it is requisite to prove that the matter he swore to was material to the question then depending.