The sum of all the forces acting on an object is called : 

• The net force is the sum of all the forces acting on an object simultaneously. 
• For example, in the following image, we can see three forces acting simultaneously on the box.
• The net force on the box will be the sum of all the forces: 40 + 8 + (- 32) = 16 N
• The force having the magnitude of 32N is taken as negative because it is exerted in the opposite direction to the other forces.

Therefore, 'Net force' is the correct answer.