A term convenient in interior ballistic theory, which is defined as the product of the number of moles of gas per gram of propellant and the adiabatic-constant-volume flame temperature. The term force comes from the Latin word for strength.

In physics force is defined by Newton's laws of motion and a force is considered that which can impose a change of velocity on a material body. In physics force is described as a quantity that produces a change in the size or shape (strength of materials) or the motion of a body.

Commonly experienced as a push or pull, force is a vector quantity, having both magnitude and direction.

Four basic types of force are known in nature. The gravitational force (Gravitation) and the electromagnetic force (Electricity; Magnetism) both have an infinite range. The strong nuclear force, or strong interaction, is a short-range force holding the atomic nucleus together, and the weak nuclear force or weak interaction, is a short-range force associated with radioactivity and particle decay.

Scientists have not been able to confirm the existence of a hypothesized fifth force, a weak force supposed to counteract gravitation.