The aim of this study is to investigate liquid consonant related phonological phenomena in a diachronic aspect in order to reveal their changing process and cause, and also to investigate the organic relationship between these phonological phenomena. This study assumes that liquid consonant related phonological phenomena are related to changes in syllable-final liquid consonants ([r]>[l]). Therefore, it firstly discusses how liquid consonants were an explosive consonant [r] in Middle Age Korean and became a lateral consonant [l] during the interval between Middle Age Korean and Modern Korean, and also the changes in syllable-final liquid consonants ([r]>[l]) are related to the proliferation of unreleased sounds.
Then continuing in Chapter 2, the study first restored the liquid consonant of Middle Age Korean into ‘r. This comes from the fact that unreleased sounds were not generalized in Ancient Korean, syllable-final liquid consonants were an explosive consonant, and the borrowed notation for liquid consonants (‘尸, 乙’) were notations for classifying morphology rather than phonology. Second, the study reveals how the syllable-final liquid consonants in Middle Age Korean are also an unreleased sound [r] and how the phonetic values of ㄹㅇ in Middle Age Korean are [r$Ø] due to traces of the syllable-final liquid consonant [r] and dropping sound. Third, we assumed that the /ㄹ/-dropping phenomenon started to appear in Ancient Korean and assumed that the sound was dropped because the distance between the tip of the tongue and the gums were too short to be perceived even though the /ㄹ/-dropping phenomenon in Middle Age Korean became articulated by explosive sounds from the stem-syllable ‘ㄹ[r]’ and chain reaction of ‘ㄹ[r]+lingual sound·dental sound’
In Chapter 3, first we discussed how the /ㄹ/-dropping phenomenon was weakened and exterminated in compound words due to the generation and proliferation of liquid consonants in Modern Korean. Also, ‘ㄷ, ㅈ’ are excluded in /ㄹ/-dropping phenomenon environments, and we assumed that the exclusion of /ㄹ/-dropping phenomenon is related to changes in final-syllable liquid consonants ([r]>[l]) and the articulation location of ‘ㅈ’ being changed from dental sound to palatal sound. Second, the study discusses how liquidization is related to the realization of final-syllable liquid consonants [l] and how the generation and proliferation of liquidization, confusion of ㄹㄴ~ㄹㄹ, etc. are related to changes in final-syllable liquid consonants ([r]>[l]).
In Chapter 4, the study firstly discusses how in Modern Korean the /ㄹ/­dropping phenomenon starts from the phonological environment ㄴ, ㅅ’ and morphological environment ‘ㅂ, ㅗ’, and the /ㄹ/­dropping form in compound words, /ㄹ/­dropping form in front of ‘ㄷ, ㅈ’, the /ㄹ/­dropping form in front of formal Korean word-final stem syllable ‘­오/옵­’ and the /ㄹ/­dropping form in front of end stem syllable ­오’ in Modern Korean are fossilized forms of language that are related to the /ㄹ/­dropping form in times before the Middle Age. Second, the study discusses how progressive liquidization and retrogressive liquidization cannot be described by the ‘mirror image principle), how the /ㄹ/­nasalization cannot be interpreted with ’syllable constraints’ and ‘/ㄹ/ distribution constraints’, and how the /ㄹ/­nasalization and retrogressive liquidization in /ㄴㄹ/-linkage is related to whether the morpheme boundary is perceived.
In Chapter 5, the study organizes the historical trend of liquid consonant related phenomena and discusses the correlation between liquid consonant related phonological phenomena, which are /ㄹ/­dropping and progressive liquidization, /ㄹ/­dropping and /으/­inserting, retrogressive liquidization and /ㄹ/­nasalization by using the components of dominant phonology and theory of analytical/non- analytical combination.
As a result of the discussions above, first, this study revealed the fact that the changing process and cause of liquid consonant related phonological phenomena are related to changes in the phonetic value of liquid consonants ([r]>[l]). Second, we were able to discover a lead for interpretation about liquid consonant related phonological phenomena that could not be explained with phonological phenomena or the phonological rules of Modern Korean. Third, by discussing the correlation between liquid consonant related phonological phenomena, establishing a system between the phenomena.