It is rare that terms have a perfect, unambiguous meaning. It is often useful to just check what definition they want to use, or state one oneself to make the discussion clear. When people use terms, the meaning often depends on what they talk about. (Where that puts black holes and dark matter can be debated.) Physicists had entered the scene, showing the nature of atoms in terms of. So they would define matter as "everything composed of elementary fermions". First, the idea of elements grew and then the atomic nature of matter was verified. Particle physicists would say that what gives matter its tendency to take up space is that it consists of fermions, those elementary particles that have half-integer spin: the details are irrelevant, but stuff with fermions (like electrons, protons and quarks) cannot be pushed together arbitrarily like light and non-fermions can. #Particles of matter freeBut black holes have mass and volume, and free electrons have mass but may not have any volume (being, perhaps, properly point-like particles). A common definition is "anything that has mass and volume", and most matter we meet is atoms. But the key thing is (1) it is localized and "small", (2) it does not have, or we do not care about, parts.Ītoms consist of electrons, protons and neutrons bound together by the electromagnetic and strong nuclear force. Depending on what you are discussing, it makes sense to regard elementary particles (those we do not know have parts, like electrons and quarks), composite particles (they have parts, like protons) or even atoms or dust (or in astronomy, even planets and stars) as particles. Particles are point-like pieces of matter.
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