Four Fundamental Interactions

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The universe we know and love exists because the fundamental particles interact, whether by decaying, annihilating, or responding to a force due to the presence of another particle (for example, during a collision). There are four interactions between particles:

Strong, weak, gravity, electromagnetism


To clarify things, here are two definitions:
Force:
The effect on a particle due to another particle's presence.
Interaction:
The forces and decays which affect a given particle.
An interaction is not the same thing as a force since the word "interaction" refers to a broader term. Although the terms are often used interchangeably, physicists prefer the word "interactions."