Atom
The word "atom" comes from the Greek (ἀτόμος) "atomos", which means indivisible or uncuttable. One of the first people to use the word "atom" is the Greek philosopher Democritus, around 400 BC. He thought that everything was made of particles called atoms, which could not be divided into smaller pieces. Some Hindu, Jain, and Buddhist philosophers also had ideas like this. Atomic theory was a mostly philosophical subject, with not much scientific investigation or study, until the early 1800s.