# What does Atom mean?

The word $\text{atom}$ derives from the Greek, $\alpha \tau o \mu o s$, which means $\text{indivisible}$ or $\text{uncuttable}$.
Some of the early Greek philosophers (circa 6th/5th century BC) proposed that the $\text{atom}$ was the smallest unit of matter. This probably derived more from philosophical notions than from experiment, and today we know that atoms are composed of protons, neutrons, and electrons.