atheistic comes from atheist + -ic, from Ancient Greek átheos ('godless'), from a- ('without') + theós ('god'). Morphologically, the word is transparent: -ic is attached to the older base named in the history, so the modern form packages an inherited or borrowed stem inside a later English derivative. In modern use, the adjective sense is "relating to or holding the belief that no god exists", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as atheism, atheist, theistic and derivatives such as atheistically, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Ancient Greek átheos, Ancient Greek theós, which anchor the explanation in named linguistic material.