**The Unit of Energy**

The unit of energy is the Joule (J).

**Explanation:**

Energy is a fundamental concept in physics that is used to describe the ability of a system to do work or create an effect. It is a scalar quantity that can exist in various forms, such as kinetic energy (energy of motion), potential energy (energy stored in an object), thermal energy (energy due to temperature difference), and many others.

The SI (International System of Units) unit for energy is the Joule, named after the English physicist James Prescott Joule. One Joule is defined as the amount of energy transferred when a force of one Newton acts on an object to move it one meter in the direction of the force.

To understand the unit of energy further, let's consider the equation for work:

Work = Force x Distance

The unit for force is the Newton (N), which is defined as the amount of force required to accelerate a one-kilogram mass by one meter per second squared. The unit for distance is the meter (m). Therefore, the unit for work is the Newton-meter (N·m), which is equivalent to the Joule (J).

Since energy and work are closely related, they share the same unit. Energy is often defined as the capacity to do work. Thus, the unit for energy is also the Joule (J).

**Summary:**

The unit of energy is the Joule (J). It is a scalar quantity that represents the capacity of a system to do work or create an effect. The Joule is defined as the amount of energy transferred when a force of one Newton acts on an object to move it one meter in the direction of the force. The unit is derived from the equation for work, which is the product of force and distance.