O

O is a letter of the Latin (Roman) alphabet, the script now used to write English and most languages of western Europe and, today, much of the world. It represents the vowel /o/. Historically it is from Phoenician ayin ('eye') by way of Greek omicron. Unlike the Hebrew and Greek alphabets, the Latin (Roman) alphabet never developed a systematic per-letter mystical or numerological tradition: Roman numerals form a separate, non-alphabetic system, so this entry stays with the letter's linguistic and historical record. The Roman alphabet is the youngest of the three historical scripts covered in this atlas: Latium adapted it around the 7th century BCE from a west Greek alphabet, reaching it through Etruscan intermediaries who had themselves taken their letters from Greek colonists settled in the bay of Naples. Latin calls each letter simply by its sound rather than by an inherited name, unlike Hebrew and Greek, and it never built an alphabetic numeral system of its own, so there is no ancient Latin counterpart to Hebrew gematria or Greek isopsephy; Roman numerals are a separate, non-alphabetic notation.

A modern practice called name numerology, drawn from a twentieth-century repeating 1-to-9 chart and commonly marketed as Pythagorean despite no documented link to Pythagoras, assigns the letter O the digit 6; a rival popular scheme, the so-called Chaldean system, assigns different digits to the same letters, so even the two modern schemes disagree with each other.

The Latin O's descent, from Phoenician ayin, meaning eye, through Greek omicron, is covered elsewhere in this atlas. As a piece of writing history, O is remarkable chiefly for how little it has changed: Phoenician ayin was already drawn as a simple circle representing an eye, and every subsequent script that borrowed it, Greek, Etruscan and Latin alike, kept the same plain circular outline, making O very likely the single most graphically stable letter in the entire Latin alphabet across roughly three thousand years of continuous use. Both the capital and lowercase O are, in most typefaces, simply the same circle at two sizes, unlike letters such as A or G whose upper and lower case diverged structurally over the centuries.

Because a circle carries no strokes to add or drop, O never generated the kind of shape splits, I and J, U and V, C and G, that reshaped several of its neighbours, and it was never pressed into service as a Roman numeral or into any of the graphic modifications, ascenders, descenders, loops, that mark the medieval and Renaissance history of most other Latin letters. The one modern complication is not historical but typographic: because O and the digit zero can look identical in many typefaces, printers and type designers have developed conventions such as a narrower oval for zero or a slash or dot through its centre, a distinction with no ancient precedent, since Rome's own numeral system, discussed elsewhere in this atlas, had no symbol for zero at all.