The horn ( or ) is a diacritic mark attached to the top right corner of the letters o and u in the Vietnamese alphabet to give ơ and ư, unrounded variants of the vowel represented by the basic letter. In Vietnamese, they are rarely considered as diacritics; but rather, the characters ơ and ư are considered as different letters from o and u. Letters with horn Encodings In Unicode, horn is encoded as a combining mark, and precomposed letters. Precombined characters in Unicode and HTML codes: and See also Hook (diacritic) Acute accent Apostrophe Latin-script diacritics Vietnamese language