A dictionary is one essence of the history, culture, belief, and industrial capabilities of a language used in a community. Instead of popping up from nowhere one day, dictionaries are the achievement of all linguistic studies being properly integrated, including phoneme, grammar, meaning, and many more. This is why a dictionary is usually called a synthetic art of linguistics. Despite such general understandings of dictionaries, only few sophisticated researches to examine the states of Korean dictionaries have been conducted in the past. This essay compares the definitions of four words, geulja(글자), munja(문자), geulssi(글씨), and ja(자), which appear in Korean dictionaries published from 1930"s. These four words all relate to the English words “letter” and “character.” In general, it is witnessed, the semantic diversities of munja itself have been gradually weakened, while geulja, munja, and geulssi have increasingly diverged themselves from one another in their meanings. Also, early dictionaries share common denominators in geulja, munja, and geulssi, whereas late dictionaries tend to minimize their differences. Though revising Korean dictionaries may require considerable time and painstaking efforts, and though consequences might not be conspicious and satisfactory within a short amount of time, it will in the long run upgrade our cultural level tremendously. As much as macroscopic researches may do, microscophic approaches, like this one, will contribute to advancing Korean lexicography.