Hanja
Although a phonetic Korean alphabet, now known as Chosŏn'gŭl or Hangul, had been created by Sejong the Great, it did not come into widespread official use until the late 19th and early 20th century. Thus, until that time it was necessary to be fluent in reading and writing Hanja in order to be literate in Korean, as the vast majority of Korean literature and most other Korean documents were written in Literary Chinese, using Hanja as its primary script. Today, a good working knowledge of Chinese characters is still important for anyone who wishes to study older texts (up to about the 1990s), or anyone who wishes to read scholarly texts in the humanities. Learning a certain number of Hanja is very helpful for understanding the etymology of Sino-Korean words, and for enlarging one's Korean vocabulary. Today, Hanja are not used to write native Korean words, which are always rendered in Hangul, and even words of Chinese origin—"Hanja-eo" ()—are written with the Hangul alphabet most of the time, with the corresponding Chinese character often written next to it in order to prevent confusion with other characters or words with the same phonetics.
Phoneme
A pair of words like "kátur" and "gátur" (above) that differ only in one phone is called a minimal pair for the two alternative phones in question (in this case, and ). The existence of minimal pairs is a common test to decide whether two phones represent different phonemes or are allophones of the same phoneme. To take another example, the minimal pair tip" and dip" illustrates that in English, and belong to separate phonemes, and ; since these two words have different meanings, English speakers must be conscious of the distinction between the two sounds. In other languages, though, including Korean, even though both sounds and occur, no such minimal pair exists. The lack of minimal pairs distinguishing and in Korean provides evidence that in this language they are allophones of a single phoneme . The word is pronounced , for example. That is, when they hear this word, Korean speakers perceive the same sound in both the beginning and middle of the word, whereas an English speaker would perceive different sounds in these two locations. Signed languages, such as American Sign Language (ASL), also have minimal pairs, differing only in (exactly) one of the signs' parameters: handshape, movement, location, palm orientation, and non-manual signal or marker. A minimal pair may exist in the signed language if the basic sign stays the same but one of these parameters changes.