The word “atom” comes from the Greek word “atomos,” which means “indivisible” or “uncuttable.” This term was coined by the ancient Greek philosopher Democritus around the 5th century BCE. He proposed that matter is composed of small, indivisible particles, which he called “atomos.” This concept laid the foundation for the modern atomic theory, though it wasn’t until much later that scientific advancements would confirm the existence of atoms as the basic building blocks of matter. The idea that atoms are indivisible has since been revised, as we now understand that atoms themselves are made up of smaller particles, such as protons, neutrons, and electrons.