The RAE dictionary tells us that nothing It is “the total nonexistence or absolute lack of all being” or also “nothing.” On the other hand, the same dictionary tells us that the vacuum in physics would be “space lacking matter.” If we stick to these definitions, the two concepts could seem synonymous in physics, but, as we are going to see, the vacuum as a space without matter can contain other ingredients, and this differentiates it from nothing. Furthermore, vacuum is a concept we work with in physics, while nothingness is not.