Chữ Hán (𡨸漢, literally "Han characters", t͡ɕɨ˦ˀ˥ haːn˧˦), chữ Nho (𡨸儒, literally "Confucian characters", t͡ɕɨ˦ˀ˥ ɲɔ˧˧) or Hán tự (漢字, haːn˧˦ tɨ˧˨ʔ) are the Vietnamese terms for Chinese characters, used to write Literary Chinese (known as Hán văn 漢文 or văn ngôn 文言 in Vietnamese) and Sino-Vietnamese vocabulary in the Vietnamese language. They were officially used in Vietnam after the Red River Delta region was incorporated into the Han dynasty and continued to be used until the early 20th century (111 BC – 1919 AD) where usage of Literary Chinese was abolished alongside the Confucian court examinations. After the conquest of Nanyue (Vietnamese: Nam Việt; chữ Hán: 南越), parts of modern day Northern Vietnam were incorporated into the Jiāozhǐ province (Vietnamese: Giao Chỉ; chữ Hán: 交趾) of the Han dynasty. It was during this era, that the Red River Delta was under direct Chinese rule for about a millennium. Around this time, Chinese characters became widespread in Northern Vietnam. Government documents, literature, and religious texts such as Buddhist sutras were all written in Literary Chinese (Vietnamese: Hán văn; chữ Hán: 漢文). From independence from China and onward, Literary Chinese still remained as the official language for writing whether if it was government documents or literature. While literature in Vietnamese (written with chữ Nôm) was the minority. Literature such as Nam quốc sơn hà (chữ Hán: 南國山河) and Long thành cầm giả ca (chữ Hán: 龍城琴者歌) being written with Chinese characters. With every new dynasty with the exception of two dynasties, Literary Chinese and thus Chinese characters remained in common usage. Several different textbooks were used traditionally to teach children chữ Hán such as Nhất thiên tự 一千字, Tam thiên tự 三千字, Ngũ thiên tự 五千字, and Tự Đức thánh chế tự học giải nghĩa ca 嗣德聖製字學解義歌. These books used rhymes alongside glosses in vernacular Vietnamese (written in chữ Nôm) to teach Chinese characters. It was until in the 20th century that Chinese characters alongside chữ Nôm began to fall into disuse.