Equilibrium is a state of balance where different forces, influences, or elements offset each other so nothing changes overall. Picture a seesaw with two kids of exactly equal weight sitting perfectly still: neither side goes up or down because the forces are in equilibrium.

In science, equilibrium appears everywhere. A book resting on a table is in equilibrium because gravity pulling it down equals the table pushing it up. In chemistry, reactions can reach equilibrium when substances form and break down at the same rate, so the overall mixture stays constant even though individual molecules keep reacting.

The word also describes balance in other areas. An ecosystem reaches equilibrium when populations of predators and prey stabilize. Your body maintains equilibrium by keeping your temperature, blood sugar, and other systems within healthy ranges. When you're spinning around and then stop suddenly, you might lose your equilibrium and feel dizzy because the fluid in your inner ear is still moving.

People use equilibrium to describe mental or emotional balance too. After something upsetting happens, you might need time to regain your equilibrium and feel steady again. Markets can be in equilibrium when supply and demand balance out.

When something is in equilibrium, opposing forces have found their balance point.