The Korean alphabet, known as Hangul in South Korea and as Chosŏn’gŭl in North Korea and China, is the alphabet that has been used to write the Korean language since the 15th century. It was created during the Joseon Dynasty in 1443, and is now the official script of both South Korea and North Korea, and co-official in the Yanbian Korean Autonomous Prefecture of China’s Jilin Province. In South Korea, Hangul is occasionally augmented by Chinese characters called Hanja; whereas in North Korea, Hanja are virtually nonexistent. In its classical and modern forms, the alphabet has 24 consonant and vowel letters. However, instead of being written sequentially like the letters of the Latin alphabet, Hangul letters are grouped into blocks, such as 한 han, each of which transcribes a syllable. That is, although the syllable 한 han may look like a single character, it is actually composed of three letters: ㅎ h, ㅏ a, and ㄴ n. Each syllabic block consists of two to six letters, including at least one consonant and one vowel. These blocks are then arranged horizontally from left to right or vertically from top to bottom. Each Korean word consists of one or more syllables, hence one or more blocks. The number of mathematically possible distinct blocks is 11,172 (see “South Korean order” below), though there are far fewer possible syllables allowed by Korean phonotactics, and not all phonotactically possible syllables occur in actual Korean words. For a phonological description, see Korean phonology.