dissension
Serious disagreement in a group that breaks their unity.
Dissension is serious disagreement or conflict within a group that disrupts unity and cooperation. When dissension breaks out in a team, members stop working together smoothly because they're arguing about important decisions or pulling in different directions.
Imagine a group project where half the students want to build a volcano and the other half insist on creating a solar system model. If they can't find a compromise and the argument gets heated, that's dissension. It's more than casual disagreement: dissension suggests discord that threatens to split the group apart or prevent it from accomplishing its goals.
The word appears often in historical and political contexts. During the American Revolution, there was dissension among the colonists about whether to fight for independence or remain loyal to Britain. Military commanders worry about dissension in the ranks, meaning soldiers doubting their leaders or disagreeing about strategy.
You might hear someone say there's “growing dissension” in an organization when disagreements start spreading and getting worse. While healthy debate can strengthen a group by surfacing good ideas, dissension weakens it by creating lasting divisions. The related word dissent means to disagree or express an opposing view, which is often valuable and important. Dissension is what happens when disagreement turns destructive.