oscillates

Oscillate means moving back and forth or swinging between two states. Think of a pendulum that swings from side to side - it's oscillating.

You might use this word when talking about how something changes frequently, like your mood on a Monday morning versus a Friday evening. Or maybe you're describing the weather in a certain place: "The temperature is always oscillating between hot and cold near the equator." Some machines can also oscillate, like fans that move back and forth to create air flow. If you ever hear someone describe how their car's engine or a musical instrument works, they might mention something about oscillation - it usually means something is moving rapidly from one state to another.