O, the fourth vowel of the modern alphabet, corresponding to the Semitic ayin, which represented a breathing and not a vowel. The Semitic form may have derived from an earlier sign representing an eye. The letter O is the fifteenth letter in the English alphabet and is classified as a vowel. It has two primary sounds: the long O sound, which is like the /O/ in open, and the short O sound, which is like the /o/ in octopus. O definition: the fifteenth letter of the English alphabet, a vowel. See examples of O used in a sentence. o - Wiktionary, the free dictionary. Jump to content. Main menu. move to sidebarhide. Navigation. Main page. Community portal. Requested entries. Recent changes. Random entry. Help. Glossary. Contact us. Special pages. Search. Appearance. Donations. Create account. Log in. Personal tools. Donations. Create account. Log in. Contents. Ó (minuscule: ó), known as O-acute, is a Latin-script character composed of the letter O and an acute accent. It is found in the Czech, Dobrujan Tatar, Emilian-Romagnol, Faroese, Hungarian, Icelandic, Kashubian, Polish, Slovak, Karakalpak, and Sorbian languages. Watch Super Simple videos ad-free on Amazon Prime Video. Just search for “Super Simple.” This super-catchy and clear alphabet song also lets children hear the letter O sound and see each letter at the beginning of five simple words paired with colorful kid-friend images. O (minuscule: o) is the fifteenth letter and the fourth vowel letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. O. O is the fifteenth (number 15) letter in the English alphabet and it has a shape of a circle. It appears after “N” and before “P”. The O with accent is a commonly used character in many languages, including Spanish, Portuguese, French, German, and Italian. Accents placed on the letter O —such as Ó, Ò, Ô, Õ, Ö —change pronunciation, meaning, or grammatical emphasis.