/ˈeɪθiˌɪzəm/
[noun] The belief that gods or a god do not exist. A person who holds this view does not accept religious explanations of the world and does not worship any higher power.
The ancient Greeks used 'atheos' not as a compliment but as a serious insult meaning 'abandoned by the gods.'
The story of the word 'atheism' begins in ancient Greece, where the compound word 'atheos' was formed by joining the prefix 'a-' (meaning 'without' or 'not') to 'theos' (meaning 'god'). But here is the fascinating twist: the early Greeks did not use this word to describe a philosophical position someone freely chose. Instead, 'atheos' carried the heavy sense of being godless in a shameful way — someone cut off from divine favour, forsaken, or impious. It was closer to a curse than a label for a school of thought.
The Greek root 'theos' itself is ancient and shared across many Indo-European languages. It connects to the Proto-Indo-European root '*dhes-', which referred to religious concepts and sacred things. This same root gave Latin its word 'festus' (meaning festive or solemn, as in a religious feast), and it is distantly related to words across European languages that touch on the sacred. The Greek 'theos' went on to become one of the most productive roots in English, giving us — through Latin and then directly from Greek — words like 'theology' (Greek 'theologia' → Latin 'theologia' → English 'theology'), 'theocracy' (Greek 'theokratia' → English 'theocracy'), and 'pantheon' (Greek 'pantheion' → Latin 'pantheon' → English 'pantheon').
The abstract noun form 'atheismos' appeared in later Greek, and from there the word passed into post-classical Latin as 'atheismus'. French scholars and writers of the Renaissance encountered it in Latin texts and brought it into French as 'athéisme' in the mid-16th century. It was in this period of religious upheaval — the Reformation shaking Europe's spiritual certainties — that having a precise word for godlessness suddenly felt very necessary. English borrowed 'atheism' directly from French 'athéisme' around the 1580s, and the related word 'atheist' appeared in English at roughly the same time, again via French 'athéiste'.
For the first century or more of its life in English, 'atheism' was almost always used as an accusation. To call someone an atheist in the 16th or 17th century was to accuse them of moral depravity and social danger, not simply of having a different philosophical view. The playwright Christopher Marlowe was accused of atheism — a charge that was essentially equivalent to being called a criminal. Even people who merely questioned orthodox doctrine could find the label thrown at them. The idea that someone could be an atheist in the calm, reasoned, modern sense — simply someone who does not believe in a god — was barely conceivable to most people at the time.
It was during the European Enlightenment of the 18th century that 'atheism' began its slow transformation into a neutral or even self-applied philosophical term. Thinkers in France, Britain, and Germany began to argue openly that reason and evidence gave no support to the existence of a deity. The French philosopher Baron d'Holbach is often considered one of the first public intellectuals to openly embrace the label. By the 19th century, figures like Charles Bradlaugh in Britain were publicly and proudly calling themselves atheists, turning the word from an insult into an identity. Today, 'atheism' sits comfortably in philosophical and everyday conversation as a straightforward description of a position — a remarkable journey for a word that began as a Greek curse.