Thermal energy is the internal energy of a system due to its temperature. It arises from the random motions of atoms and molecules within the system.
The energy possessed by an object due to its motion, given by $\frac{1}{2}mv^2$ where $m$ is mass and $v$ is velocity.
A fundamental principle stating that total energy in an isolated system remains constant over time.
A measure of the average kinetic energy of particles in a substance, often measured in degrees Celsius (°C), Kelvin (K), or Fahrenheit (°F).