When two or more than two forces act on a body, they are said to form a system of forces. Following are the various system of forces:

1.    Coplanar forces. The forces, whose lines of action lie on the same plane are known as coplanar forces.

2.    Concurrent forces. The forces, which meet at one point, are known as concurrent forces.

3.    Coplanar concurrent forces. The forces, which meet at one point and their lines of action also lie on the same plane, are called coplanar concurrent forces.

4.    Coplanar non-concurrent forces. The forces, which do not meet at one point but their lines action lie on the same plane, are known as coplanar non-concurrent forces.

5.    Non-coplanar concurrent forces. The forces, which meet at one point but their lines of action do not lie on the same plane are known as non-coplanar concurrent forces.

6.    Non-coplanar non-concurrent forces. The forces, which do not meet at one point and their lines of actions do not lie on the same plane are called non-coplanar non-concurrent forces.