Middle Korean is the period in the history of the Korean language succeeding Old Korean and yielding in 1600 to the Modern period. The boundary between the Old and Middle periods is traditionally identified with the establishment of Goryeo in 918, but some scholars have argued for the time of the Mongol invasions of Korea. Middle Korean is often divided into Early and Late periods corresponding to Goryeo and Joseon respectively. It is difficult to extract linguistic information from texts of the Early period, which are written using adaptations of Chinese characters. The situation was transformed in 1446 by the introduction of the Hangul alphabet, so that Late Middle Korean provides the pivotal data for the history of Korean.
Script and phonology
Hangul letters correspond closely to the phonemes of Late Middle Korean. The romanization most commonly used in linguistic writing on the history of Korean is the Yale romanization devised by Samuel Martin, which faithfully reflects the Hangul spelling. The tensed stops pp, tt, cc and kk are distinct phonemes in modern Korean, but in LMK they were allophones of consonant clusters. The tensed fricative hh only occurred in a single verb root, hhye- 'to pull', and has disappeared in Modern Korean. Late Middle Korean had a limited and skewed set of initial clusters: sp-, st-, sk-, pt-, pth-, ps-, pc-, pst- and psk-. It is believed that they resulted from syncope of vowels o or u during the Middle Korean period. For example, the Jilin leishi has *posol 'rice', which became LMK psól and modern ssal. A similar process is responsible for many aspirated consonants. For example, the Jilin leishi has *huku- 'big', which became LMK and modern khu. Late Middle Korean had seven vowels: The precise phonetic values of these vowels are controversial. Six of them are still distinguished in modern Korean, but only the Jeju language has a distinct reflex of o. In other varieties it has merged with a in the first syllable of a word and u elsewhere. LMK had rigid vowel harmony, described in the Hunminjeongeum by dividing the vowels into three groups:
yang : a, o and wo
yin : e, u and wu
neutral: i
Yang and yin vowels could not occur in the same word, but could co-occur with the neutral vowel. The phonetic dimension underlying vowel harmony is also disputed. Lee Ki-Moon suggested that LMK vowel harmony was based on vowel height. Some recent authors attribute it to advanced and retracted tongue root states. Loans from Middle Mongolian in the 13th century show several puzzling correspondences, in particular between Middle Mongolian ü and Korean u. Based on these data and transcriptions in the Jilin leishi, Lee Ki-Moon argued for a Korean Vowel Shift between the 13th and 15th centuries, chain shifts involving five of these vowels:
> > >
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William Labov found that this proposed shift followed different principles to all the other chain shifts he surveyed. Lee's interpretation of both the Mongolian and Jilin leishi materials has also been challenged by several authors. LMK also had two glides, y and w :
A y on-glide could precede four of the vowels, indicated in Hangul with modified letters: ya ㅑ, ye ㅕ, ywo ㅛ and ywu ㅠ.
A w on-glide could precede a or e, written with a pair of vowel symbols: wa ㅘ and we ㅝ.
A y off-glide could follow any of the pure vowels except i or any of the six onglide-vowel combinations, and was marked by adding the letter i. In modern Korean the vowel-offglide sequences have become monophthongs.
Early Hangul texts distinguish three pitch contours on each syllable: low, high and rising. The rising tone may have been longer in duration, and is believed to have arisen from a contraction of a pair of syllables with low and high tone. LMK texts do not show a clear distinctions after the first high or rising tone in a word, suggesting that the language had a pitch accent rather than a full tone system.
Vocabulary
Although some Chinese words had previously entered Korean, Middle Korean was the period of the massive and systematic influx of Sino-Korean vocabulary. As a result, over half the modern Korean lexicon consists of Sino-Korean words, though they account for only about a tenth of basic vocabulary. Classical Chinese was the language of government and scholarship in Korea from the 7th century until the Gabo Reforms of the 1890s. After King Gwangjong established the gwageocivil service examinations on the Chinese model in 958, familiarity with written Chinese and the Chinese classics spread through the ruling classes. Korean literati read Chinese texts using a standardized Korean pronunciation, originally based on Middle Chinese. They used Chinese rhyme dictionaries, which specified the pronunciations of Chinese characters relative to other characters, and could thus be used to systematically construct a Sino-Korean reading for any word encountered in a Chinese text. This system became so entrenched that 15th-century efforts to reform it to more closely match the Chinese pronunciation of the time were abandoned. The prestige of Chinese was further enhanced by the adoption of Confucianism as the state ideology of Joseon, and Chinese literary forms flooded into the language at all levels of society. Some of these denoted items of imported culture, but it was also common to introduce Sino-Korean words that directly competed with native vocabulary. Many Korean words known from Middle Korean texts have since been lost in favour of their Sino-Korean counterparts, including the following.
