conflict — Conflict is serious disagreement and argument about something important. If two people or groups are in conflict, they have had a serious disagreement or argument and have not yet reached agreement.
argument — An argument is a statement or set of statements that you use in order to try to convince people that your opinion about something is correct.
clash — When people clash, they fight, argue, or disagree with each other.
confrontation — A confrontation is a dispute, fight, or battle between two groups of people.
contention — Someone's contention is the idea or opinion that they are expressing in an argument or discussion.
controversy — Controversy is a lot of discussion and argument about something, often involving strong feelings of anger or disapproval.
difference — the state or relation of being different; dissimilarity: There is a great difference between the two.
disagreement — the act, state, or fact of disagreeing.
discord — lack of concord or harmony between persons or things: marital discord.
dissension — strong disagreement; a contention or quarrel; discord.
dissent — to differ in sentiment or opinion, especially from the majority; withhold assent; disagree (often followed by from): Two of the justices dissented from the majority decision.