In the natural world, there are many forces. We feel some of them in our daily lives, like- heat, friction, viscosity, electricity, gravity, and many others, while there are other forces that we do not feel in our daily lives like- radioactivity or the binding force of the atomic nucleus. Among the different forces (or interactive forces), the majority are interactions in physical systems that are reducible to basic (or fundamental) interactions, while a few forces are not reducible. They are the fundamental forces of nature.

There ‘were’ five known fundamental forces, until the middle of the 19th century- gravity, magnetism, electricity, strong and weak force. Magnetism and electricity have been unified into a single force- electromagnetism in the middle of the nineteenth century. Again, in the 20th century, scientists discovered that electromagnetism and weak forces are different facets of a single, more fundamental electroweak force. The characteristics of the unified electroweak force, including the strength of the interactions and the properties of the carrier particles, are summarized in the Standard Model of particle physics.