To unify means to bring separate parts together into a single whole. When a teacher unifies the class after recess, she gathers everyone from different corners of the playground back into one group. When a coach unifies her team, she helps players work together toward a common goal instead of pursuing their own individual glory.

Unification can happen with ideas, too. A scientist might unify different theories by showing how they're all parts of one bigger explanation. A country becomes unified when its regions and people see themselves as one nation rather than separate groups. The United States was unified under the Constitution, bringing thirteen states together under one federal government.

When something becomes unified, what was once many becomes one. A unifying force is anything that brings people or things together: a shared goal, a common interest, or even a crisis that makes everyone work as a team. The opposite is to divide or fracture something into separate pieces.