Chapter 2 discusses some of the most salient and yet persistently controversial and significant phenomena in Korean phonology: lenis obstruent voicing, stop neutralization, consonant cluster simplification, consonant assimilation, consonantal fortition, Saisiot, vowel deletion and insertion, vowel devoicing and assimilation, monophthongization, vowel harmony, and sound symbolism. The chapter focuses on the Seoul Standard Dialect. One salient and recurrent theme is the theoretical issue of the relative strength of each sound, both inherent and in its environment. Some sounds are held to be “stronger” than others; we see that these sounds are exploited not only in sound symbolism but also in the application or non-application of certain rules. Boundaries play a significant role in Korean phonology and are analyzed as prosodic units in contemporary analyses. The Korean-specific basis of articulation, particularly obligatory unreleasing, results in many interesting weakening effects, including consonant cluster simplification, various assimilatory phenomena, and various consonant and vowel insertions by backward generalizations.