The Korean alphabet, called Hangul, is the only major writing system in human history with a known inventor and a documented design rationale — created in 1443 by King Sejong of the Joseon dynasty, who designed each consonant to physically represent the position of the tongue and lips during the corresponding sound, and published a companion document explaining exactly why each letter looked the way it did

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Nobody knows who invented the letter A. Nobody knows who invented the letter B, or C, or any other letter of any writing system used by any other major language on Earth. The Latin alphabet evolved from the Etruscan script over the course of several centuries, with no identifiable inventor and no contemporaneous documentation of why its letters take their specific shapes. Etruscan, in turn, derived from a variant of the Greek alphabet, which derived from Phoenician, which derived from Proto-Sinaitic, which derived (probably) from selected Egyptian hieroglyphic signs adapted by Semitic-speaking workers in the Sinai approximately 4,000 years ago. The Chinese writing system emerged from oracle-bone inscriptions across approximately 3,000 years of gradual development. The Devanagari script (used for Sanskrit and Hindi) developed from the Brahmi script across approximately 2,000 years. Arabic developed from Nabataean across several centuries. In every case, the writing system was the cumulative product of incremental adaptations across many generations of anonymous users, and the specific shapes of the individual letters are explicable only by tracing the historical lineage of each character through its prior forms. Hangul is the only major writing system that does not work this way. Hangul was designed, deliberately, by a single identifiable person, for an identifiable reason, in an identifiable year, with an identifiable theoretical framework — and the explanatory document King Sejong commissioned and approved has survived intact across the subsequent 583 years and is readable today.

According to Britannica’s reference summary of Hangul’s history, design, and place in Korean culture, the motivation for the project was straightforwardly egalitarian by the standards of 15th-century Confucian East Asia. Sejong’s preface to the 1446 Hunminjeongeum begins with the observation that "the sounds of our country’s language are different from those of the Middle Kingdom and are not confluent with the sounds of characters" — meaning that the Chinese characters (Hanja) that Korea had been using as a borrowed writing system for several centuries were structurally unsuited to the very different phonology of the Korean language, and that the resulting difficulty of learning to read had restricted literacy to the small fraction of the population (perhaps three to five percent, concentrated among the male aristocratic yangban class) that could afford the years of study required to master Hanja. The remainder of the Korean population — peasants, women, artisans, the lower bureaucracy, monks of less prestigious Buddhist orders — was, in essential respects, structurally excluded from written communication. Sejong’s stated goal was to design a writing system simple enough that "a wise man can learn it in a morning, and even a fool can learn it in ten days."

How the letters were designed

The design principles that produced Hangul’s letter shapes were explained in detail in the Hunminjeongeum Haerye and have been verified by modern linguistic analysis as essentially correct. The basic consonants are stylised diagrams of the articulatory organs producing each sound. As detailed in a Korea100 reference summary maintained by the Academy of Korean Studies on the origins and historical use of Hangul, the consonant ㄱ (a velar stop, pronounced g or k) is shaped to represent the position of the root of the tongue blocking the back of the throat at the moment the sound is produced. The consonant ㄴ (the dental n) is shaped to represent the tip of the tongue touching the upper alveolar ridge. The consonant ㅁ (the bilabial m) is shaped as a square, representing the closed lips. The consonant ㅅ (a fricative s) is shaped to represent the front teeth. The consonant ㅇ (originally a velar nasal, now a silent placeholder for vowel-initial syllables) is shaped as a circle, representing the open throat. Each of these five basic shapes corresponds to one of five articulatory categories — guttural, lingual, labial, dental, glottal — and the remaining consonants of the alphabet are systematically derived from these basic shapes by the addition of strokes that encode increased aspiration or other phonological modifications.

The vowels were designed on a different principle. Sejong’s framework drew on Confucian cosmology, which divided existence into three primary categories: Heaven, Earth, and Human. The basic vowels of Hangul correspond to these categories visually: a small dot (representing Heaven,...