Hangul
Letter design

Scripts typically transcribe languages at the level of morphemes (logographic scripts like Hanja), of syllables (syllabaries like kana), of segments (alphabetic scripts like the Latin script used to write English and many other languages), or, on occasion, of distinctive features. The Korean alphabet incorporates aspects of the latter three, grouping sounds into syllables, using distinct symbols for segments, and in some cases using distinct strokes to indicate distinctive features such as place of articulation (labial, coronal, velar, or glottal) and manner of articulation (plosive, nasal, sibilant, aspiration) for consonants, and iotation (a preceding i- sound), harmonic class and i-mutation for vowels.

For instance, the consonant ㅌ ṭ is composed of three strokes, each one meaningful: the top stroke indicates ㅌ is a plosive, like ㆆ ʔ, ㄱ g, ㄷ d, ㅈ j, which have the same stroke (the last is an affricate, a plosive–fricative sequence); the middle stroke indicates that ㅌ is aspirated, like ㅎ h, ㅋ ḳ, ㅊ ch, which also have this stroke; and the bottom stroke indicates that ㅌ is alveolar, like ㄴ n, ㄷ d, and ㄹ l. (It is said to represent the shape of the tongue when pronouncing coronal consonants, though this is not certain.) Two obsolete consonants, ㆁ and ㅱ, have dual pronunciations, and appear to be composed of two elements corresponding to these two pronunciations: ~silence for ㆁ and ~ for ㅱ.

With vowel letters, a short stroke connected to the main line of the letter indicates that this is one of the vowels that can be iotated; this stroke is then doubled when the vowel is iotated. The position of the stroke indicates which harmonic class the vowel belongs to, light (top or right) or dark (bottom or left). In the modern alphabet, an additional vertical stroke indicates i mutation, deriving ㅐ, ㅚ, and ㅟ from ㅏ, ㅗ, and ㅜ. However, this is not part of the intentional design of the script, but rather a natural development from what were originally diphthongs ending in the vowel ㅣ. Indeed, in many Korean dialects, including the standard dialect of Seoul, some of these may still be diphthongs. For example, in the Seoul dialect, ㅚ may alternatively be pronounced, and ㅟ. Note: ㅔ as a morpheme is ㅓ combined with ㅣ as a vertical stroke. As a phoneme, its sound is not by i mutation of ㅓ.

Beside the letters, the Korean alphabet originally employed diacritic marks to indicate pitch accent. A syllable with a high pitch (거성) was marked with a dot (〮) to the left of it (when writing vertically); a syllable with a rising pitch (상성) was marked with a double dot, like a colon (〯). These are no longer used, as modern Seoul Korean has lost tonality. Vowel length has also been neutralized in Modern Korean and is no longer written.
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