The rock cycle is a system that shows how rocks change or transform over time. So, basically how rocks transform from one stage to another.  The rock stages are Metamorphic, Igneous, and Sedimentary rock.

A variable is something that can be changed in an experiment. For ex: You're growing a tomato plant and you put some plant food on it. The plant grows taller the next week. The variable is the plant's height. This is true because the plant heights changes when you put the food  in it.

A simple circuit has one power source, one lightbulb, and one switch. A switch makes a simple circuit much easier to

Wind is the movement of air near Earth’s surface. Wind can be a gentle breeze or a strong gale. The most powerful wind happens during storms called tornadoes, cyclones, and hurricanes. Changes in the temperature of air, land, and water cause wind.  The global pattern of prevailing winds is caused by the uneven heating of Earth’s surface.As prevailing winds blow across the ocean, they create surface currents in the water. Both prevailing winds and surface currents appear to curve due to Earth’s rotation. This is known as the Coriolis effect.

Any push or pull that causes an object to move, stop, or change speed, direction, or shape. For example, take baseball physics. When the pitcher throws the baseball at the batter, we notice that the ball is moving at a certain speed at a certain time. Let's say it's going toward the batter at 150 km (92 miles per hour).