【Deny】 , 【gainsay】 , 【contradict】 , 【negative】 , 【traverse】 , 【impugn】 , 【contravene】  are comparable as meaning, when they refer to an act, to declare something untrue, untenable, or unworthy of consideration or, when they refer to a condition, to go counter to what is true or to the facts as they are.

【Deny】 commonly implies a refusal and usually a firm or outspoken refusal to accept as true, to grant or concede, or to acknowledge the existence or claims of.

In the reflexive form  【deny】 usually implies abstinence or renunciation often, but not necessarily, for religious or moral reasons.

【Gainsay】 is somewhat formal or literary; it implies opposition, usually by way of disputing the truth of what another has said.

【Contradict】  differs from 【gainsay】 not only in usually implying a more open or a flatter denial of the truth of an assertion but also in commonly suggesting that the contrary of the assertion is true or that the statement is utterly devoid of truth; thus, " to 【contradict】 a rumor" is a stronger expression than "to 【deny】 a rumor"; one may 【contradict】 (never in this sense 【deny】 ) a person, whereas one may 【deny】 or 【contradict】  (the stronger term) an assertion of his.

【Contradict】 is also used without implication of a spoken or written denial: it then suggests that an assertion, a doctrine, or a teaching runs counter to something else, and therefore either it cannot be true or the other must be false.

【Negative】 is usually a much ilder term than those which precede; often it implies merely a refusal to assent to something (as a suggestion, a proposition, a nomination, or a bill).

When the idea of going counter to is uppermost, 【negative】 usually implies disproof.

【Traverse】 occurs chiefly in legal use and implies a formal denial (as of the truth of an allegation or the justice of an indictment).

【Impugn】 usually retains much of its basic implication of attacking and carries the strongest suggestion of any of these terms of directly disputing or questioning or of forcefully contradicting a statement, proposition, or less often a person; it sometimes connotes prolonged argument in an attempt to refute or confute.

【Contravene】 implies strongly a coming into conflict but less strongly than the other terms an intentional opposition, suggesting rather some inherent incompatibility.