It is defined as any external force acting upon a machine part.
The following four types of the load are important from the subject point of view:
1. Dead or steady load:
A load is said to be a dead or steady load, when it does not change in magnitude or direction.
2. Live or variable load:
A load is said to be a live or variable load, when it changes continually.
3. Suddenly applied or shock loads:
A load is said to be a suddenly applied or shock load, when it is suddenly applied or removed.
4. Impact load:
A load is said to be an impact load, when it is applied with some initial velocity.
Note: A machine part resists a dead load more easily than a live load and a live load more easily than a shock
A textbook of Machine Desigh by R.S.Khurmi and J.K.Gupta