The Vietnamese alphabet (Vietnamese: chữ Quốc ngữ, chữ Nôm: 𡨸國語, lit. 'script of the national language', IPA: [t͡ɕɨ˦ˀ˥ kuək̚˧˦ ŋɨ˦ˀ˥]) is the modern writing script for the Vietnamese language. It is a Latin-based script whose spelling conventions are derived from the orthography of Romance languages such as Portuguese, Italian, and French. It was originally developed by Francisco de Pina and other Jesuit missionaries in the early 17th century.
The Vietnamese alphabet contains 29 letters, including 7 letters using four diacritics: ⟨ă⟩, ⟨â⟩, ⟨ê⟩, ⟨ô⟩, ⟨ơ⟩, ⟨ư⟩, and ⟨đ⟩. There are an additional 5 diacritics used to designate tone (as in ⟨à ⟩, ⟨á⟩, ⟨ả⟩, ⟨ã⟩, and ⟨ạ⟩). The complex vowel system and the large number of letters with diacritics, which can stack twice on the same letter (e.g. nhất meaning 'first'), makes it easy to distinguish the Vietnamese orthography from other writing systems that use the Latin alphabet.