U+0309 "̉" Combining Hook Above Unicode Character

U+0309 "̉" Combining Hook Above is a diacritical mark used in the Latin script, primarily to indicate a specific tonal or phonetic modification, most famously in the Vietnamese language where it forms the đấu hỏi or falling rising tone. As a combining character, it is designed to be placed directly above a base letter, such as a, e, or o, altering its pronunciation without introducing a separate glyph. This mark is essential for accurate orthography and typography in Vietnamese, distinguishing meanings between words that differ only by tone, and it must follow the base character in text to render correctly in digital systems.