天乙 (*HANOr(h))
In Old Korean orthography, native terms with clear Chinese equivalents are usually written with an initial Chinese character (logogram) glossing the meaning of the word, followed by one or more Chinese characters (phonograms) that transcribe the final syllable or coda consonant of the term. In the case of 天乙, the first character shows that this is the native Old Korean word for “heaven”, and the subsequent character(s) show(s) that the coda consonant of this word is *-r. Because the semantics and the final phoneme(s) match, the word is conventionally reconstructed as *HANOr, the ancestor of Middle Korean 하ᄂᆞᆶ〮 (Yale: hànólh). Note that the reconstruction was not necessarily the actual pronunciation. Rather, it should simply be considered as a method of representing an Old Korean form phonetically by using its Middle Korean reflex.
According to scholarly convention, the elements of the reconstruction which are not directly represented by phonograms are given in capital letters. This allows readers to identify what part of the reconstruction is attested and what part is applied retroactively from the Middle Korean reflex. Because transcriptions of reconstructed Old Korean generally make only the phonological distinctions that exist in Middle Korean, and Middle Korean merged Old Korean *r and *l unconditionally, the phonologically imprecise reconstruction *HANOl is also commonly seen.
The accuracy of the reconstruction *HANOr is supported by the Jilin Leishi, a twelfth-century wordlist of Korean terms as transcribed by a Chinese visitor. The Leishi writes the Old Korean word for Chinese 天 (tiān, “sky; heaven”) as 漢捺. The sequences are reconstructed in Late Middle Chinese as roughly */han nɑt̚/. Leishi *-t usually transcribes Old Korean *-r or *-l, and thus the Old Korean noun for "sky; heaven" must have been pronounced similar to */hannar/.