【Reason】 ,  【ground】 ,  【argument】 ,  【proof】  are comparable when they mean a point or series of points offered or capable of being offered in support of something questioned or disputed.

【Reason】  usually implies the need of justification, either to oneself or another, of some practice, action, opinion, or belief; it is usually personal in its reference; thus, a father asks the  【reason】  for his son′s disobedience; a person gives the reasons for his preference.  【Reason】 is often applied to a motive, consideration, or inducement which one offers in explanation or defense.

【Ground】  is often used in place of  【reason】  because it too implies the intent to justify or defend. When, however, the emphasis is on evidence, data, facts, or logical reasoning rather than on motives or considerations,  【ground】  is the acceptable word; thus, the reasons for a belief may explain why it is held, but the grounds for it give evidence of the validity of that belief; a scientist presents the grounds for his conclusion.

【Ground】  also suggests more solid support in fact and therefore greater cogency and objectivity than  【reason】 ; thus, one may speak of frivolous or of trumped-up reasons but not grounds .

【Argument】 stresses the intent to convince another or to bring him into agreement with one′s view or position. It can imply the use of evidence and reasoning in the making and stating of a point in support of one′s contention, but often it suggests reasoning without reference to fact .

【Proof】  in much of its use (see  【proof】  under PROVE ) emphasizes not an intent but an effect: that of conclusive demonstration; therefore, a  【proof】 is a piece of evidence (as a fact or a document) or of testimony (as of a witness or expert) or an 【argument】 that evokes a feeling of certainty in those who are to be convinced.