Definition:Valid Argument

A valid argument is an argument in which the premises provide conclusive reasons for the conclusion.

Sometimes the term sound is found instead of valid.

When a proof is valid, we may say one of the following:
 * The conclusion follows from the premises;
 * The premises entail the conclusion;
 * The conclusion is true on the strength of the premises;
 * The conclusion is drawn from the premises;
 * The conclusion is deduced from the premises;
 * The conclusion is derived from the premises.

A valid argument whose premises are all accepted as true is known as a proof.