What is the scientific term for "everything that exists"?

The scientific term for “everything that exists” is the universe. It includes all space and time, matter and energy, and the physical structures formed from them, from subatomic particles to galaxies.

Modern cosmology says the universe has been expanding since the Big Bang, which occurred about 13.8 billion years ago. The universe we can observe is only a portion of the whole, because light from more distant regions has not had enough time to reach Earth.

The word “cosmos” is often used as a near-synonym, especially when emphasizing the universe as an ordered system. “Multiverse” is different: it refers to hypothetical collections of universes, while the universe traditionally means the totality of physical existence. The phrase “theory of everything” is also commonly confused with the answer; it describes a proposed fundamental theory, not everything that exists.