Other sources include inscriptions on steles and wooden tablets, glosses to Buddhist sutras, and the transcription of personal and place names in works otherwise in Classical Chinese.
However, Old Korean is thought to have differed from its descendants in certain typological features, including the existence of clausal nominalization and the ability of inflecting verb roots to appear in isolation.
[8] Korean syntax and morphemes are visibly attested for the first time in Silla texts of the mid- to late sixth century,[9][10] and the use of such vernacular elements becomes more extensive by the Unified period.
[12] After another century of conflict, the kings of Silla allied with Tang China to destroy the other two kingdoms—Baekje in 660, and Goguryeo in 668—and to unite the southern two-thirds of the Korean Peninsula under their rule.
Lee Ki-Moon and S. Roberts Ramsey argue in 2011 that evidence for mutual intelligibility is insufficient, and that linguists ought to "treat the fragments of the three languages as representing three separate corpora".
By the early tenth century, the Korean Peninsula was once more divided into three warring polities: the rump Silla state, and two new kingdoms founded by local magnates.
Idiosyncratic Chinese vocabulary suggestive of vernacular influence is found even in the oldest surviving Silla inscription, a stele in Pohang dated to either 441 or 501.
[38] The Imsin Vow Stone, raised in either 552 or 612,[9] is also illustrative: Other sixth-century epigraphs that arrange Chinese vocabulary using Korean syntax and employ Chinese semantic equivalents for certain Korean functional morphemes have been discovered, including stelae bearing royal edicts or celebrating public works and sixth-century rock inscriptions left at Ulju by royals on tour.
[44] Mokgan are valuable primary sources because they were largely written by and reflect the concerns of low-ranking officials, unlike other texts that are dominated by the high elite.
[46] With the development of infrared imaging science in the 1990s, it became possible to read many formerly indecipherable texts,[47] and a comprehensive catalog of hitherto discovered slips was published in 2004.
[10] The only Korean-language literature that survives from Silla are vernacular poems now called hyangga (Korean: 향가; Hanja: 鄕歌), literally "local songs".
Fourteen are recorded in the Samguk yusa, a history compiled in the 1280s by the monk Iryeon,[57] along with prose introductions that detail how the poem came to be composed.
[63][64] Nam Pung-hyun nevertheless considers most of the Samguk yusa poems to be reliable sources for Old Korean because Iryeon would have learned the Buddhist canon through a "very conservative" dialect and thus fully understood the Silla language.
[65] Other scholars, such as Park Yongsik, point to thirteenth-century grammatical elements in the poems while acknowledging that the overall framework of the hyangga texts is Old Korean.
[68][69] The earliest reconstructions by a Korean scholar were made by Yang Chu-dong in 1942 and corrected many of Ogura's errors, for instance properly identifying 只 as a phonogram for *-k.[70] The analyses of Kim Wan-jin in 1980 established many general principles of hyangga orthography.
[71][72] Interpretations of hyangga after the 1990s, such as those of Nam Pung-hyun in the 2010s, draw on new understandings of early Korean grammar provided by newly discovered Goryeo texts.
[88] The eighth-century Japanese history Nihon Shoki also preserves a single sentence in the Silla language, apparently some sort of oath, although its meaning can only be guessed from context.
[109] In the eighth-century poem Heonhwa-ga given below, for instance, the inflected verb 獻乎理音如 give-INTENT-PROSP-ESSEN-DEC begins with the SAL 獻 "to give" and is followed by three PAPs and a final SAP that mark mood, aspect, and essentiality.
[143] However, Lee Ki-Moon and S. Robert Ramsey note that in the Old Korean period, idu and hyangchal were "different in intent" but involved the "same transcription strategies".
[146] Fifteenth-century Middle Korean was a tonal or pitch accent language whose orthography distinguished between three tones: high, rising, and low.
[149] Phonetic glosses in Silla Buddhist texts show that as early as the eighth century, Sino-Korean involved three tonal categories and failed to distinguish rising and departing tones.
Middle Korean closed syllables with bimoraic "rising tone" reflect an originally bisyllabic CVCV form in which the final vowel was reduced,[161] and some linguists propose that Old Korean or its precursor originally had a CV syllable structure like that of Japanese, with all clusters and coda consonants forming due to vowel reduction later on.
[172] The Middle Korean series of aspirated stops and affricates developed from mergers of consonant clusters involving /h/ or a velar obstruent, which in turn had formed from the loss of intervening vowels.
[177] On the other hand, Ki-Moon Lee and S. Roberts Ramsey argue that Silla orthography confirms the existence in Old Korean of at least the dental aspirates as phonemes.
[175] Meanwhile, Nam Pung-hyun believes that Old Korean had *kʰ and *tsʰ but may have lacked *pʰ and *tʰ, while noting that the functional load of the aspirates was "extremely low".
Vovin considers this claim "unacceptable" and "counterintuitive", especially given the reconstructed Old Chinese pronunciations of both characters, and suggests instead that 尸 represented /l/ while 乙 stood for a rhotic.
[190] The mokgan data, discussed in Lee Seungjae 2017, suggests that multiples of ten may have been referred to with Chinese loanwords but that indigenous terms were used for single-digit numbers.
The Samguk yusa narrative recounts that Lady Suro, the beautiful wife of a local magistrate, once came upon a cliff a thousand zhang high topped by azalea blooms.
Upon hearing her words, however, an old man who had been leading a cow beside the cliff presented the flowers to her while singing the Heonhwa-ga.[201][202] Nam Pung-hyun considers the song "of relatively easy interpretation" due to its short length, the context provided, and its consistent hunju eumjong orthography.
[63][o] 紫布岩乎邊希執音乎手母牛放敎遣吾肸不喩慚肸伊賜等花肸折叱可獻乎理音如ca pho am ho pyen huy cip um ho su mo wu pang kyo kyen o hil pwul ywu cham hil i sa tung hoa hil cel cil ka hen ho li um ye ᄃᆞᆯ뵈 바희 ᄀᆞᆺᄋᆡ 잡ᄋᆞᆷ 혼 손 암쇼 놓이시고 나ᄅᆞᆯ 안디 븟그리ᄉᆞᆫ ᄃᆞᆫ 곶ᄋᆞᆯ 것거 받오리ᇝ다 NMR: nominalizer INTENT: intentional mood ESSEN: essentiality tólpoy pahuy kós-óy cap-óm [ho]-n son amsyo noh-kisi-ko na-lól anti puskuli-só-n tó-n koc-ól kesk-e pat-o-li-ms-ta purple rock edge-LOC hold-DUR [do]-NMR hand cow-ACC let.go-HON-CONJ I-ACC NEG be.ashamed-HON-NMR fact-TOP flower-ACC pick-INF give-INTENT-PROSP-ESSEN-DEC Beside the purple rock [of azaleas] You made me let loose the cows [because of your beauty] And if you do not feel ashamed of me I shall pick a flower and give it to you.