Energy of a body is its capacity to do work.
It is measured by the total amount of work that a body can do.
SI unit of energy is Joule.
Its dimensional formula is #[ML^2 T^(-2)]#
There are different forms of energy like mechanical energy, heat energy, light energy, sound energy, electric energy, magnetic energy, chemical energy, nuclear energy, etc.
It is important to note :
Mechanical energy = Kinetic energy + Potential energy
Mechanical energy = #1/2 mv^2# + mgh