* "A-" means "not" or "without."
* "tomos" means "cut" or "divided."
Therefore, "atomos" literally means "uncuttable" or "indivisible."
The Greek philosopher Democritus (c. 460 – 370 BC) first proposed the idea that matter was made up of indivisible particles, which he called "atomos." He believed that all matter was composed of these tiny, solid particles, and that different substances were made up of different arrangements of these particles.
While Democritus's theory was based on philosophical reasoning and not empirical evidence, his idea laid the groundwork for the later development of modern atomic theory.
It wasn't until the 19th century that scientists like John Dalton began to develop a more rigorous and scientific understanding of atoms, leading to the development of the modern atomic theory.