Why learning Korean continues after you start reading Hangul

Why does ‘옷’ sound like [오시] when ‘이’ is added? Why do ‘학교에 가요’ (go to school) and ‘학교에서 공부해요’ (study at school) use different particles? Even people who know the Hangul letters encounter new questions as they read and speak Korean. The principles for combining letters, the way words are pronounced and the rules that create meaning within sentences are connected, but each must be learned. Looking at the design of the script on Hangul Day makes it clearer why studying Korean continues after learning its letters.

The three letters that form the syllable ‘한’

‘한글’ looks like two blocks, but separating them reveals ㅎ·ㅏ·ㄴ and ㄱ·ㅡ·ㄹ. Hangul groups letters representing consonants and vowels into syllable units in this way. This is called moasseugi, or writing letters together in syllable blocks. Learners used to placing Latin letters side by side may notice this difference first. National Institute of Korean Language, ‘The structure of Hangul’

Each letter also has a designated place within a syllable. In ‘한’, ㅎ is the initial consonant, ㅏ the vowel and ㄴ the final consonant, or batchim. Some syllables have no final consonant. The syllables ‘우’ and ‘유’ in ‘우유’ (milk) each consist of ㅇ and a vowel; here, ㅇ in the initial position has no consonant sound of its own. Understanding this structure lets learners examine where familiar letters are placed, instead of memorizing ‘한’, ‘글’, ‘우’ and ‘유’ as entirely new pictures. National Institute of Korean Language, ‘The structure of Hangul’

Letter shapes reflect relationships between sounds

The basic consonants ㄱ·ㄴ·ㅁ·ㅅ·ㅇ were created by modeling the shapes of speech organs. The shape of ㅁ is based on closed lips, while ㄴ is based on the tongue tip touching the upper gums. Other letters were designed from these basic forms, as when a stroke is added to ㄱ to make ㅋ. The relationship between shape and sound can also be seen in ㄱ·ㅋ·ㄲ, which learners study today. These three consonants are articulated at the same place in the mouth but are distinguished as plain, aspirated and tense sounds. National Institute of Korean Language, ‘Consonants’

The vowels also reflected the philosophical ideas of the time. The original basic vowels ㆍ·ㅡ·ㅣ symbolized heaven, earth and the human being, respectively. Other vowel letters were made by combining these elements. Placing ㆍ above and below ㅡ led to ㅗ·ㅜ; placing it to the right and left of ㅣ led to ㅏ·ㅓ. In today's letters, the original dot looks like a short stroke. The same principle of combination is visible when ㅗ and ㅏ are joined to write ㅘ. The resemblance between related letters is thus no accident. National Institute of Korean Language, ‘Vowels’

The same ‘옷’ sounds different depending on what follows

Read on its own, ‘옷’ (clothes) is pronounced [옫], but adding the particle ‘이’ produces [오시]. This happens because the final consonant ㅅ is pronounced as the initial sound of the following syllable. In ‘옷도’, the final consonant sounds like [ㄷ] and the following ㄷ becomes tense, producing [옫또]. The written form ‘옷’ remains the same, but speech reflects its relationship with the sounds that follow. Learning how sounds change when letters are connected takes learners one step beyond knowing the alphabet. Korean Basic Dictionary, ‘옷’ · National Institute of Korean Language, explanation of the Standard Pronunciation Rules

‘학교에’ and ‘학교에서’: short particles define relationships in a sentence

Even in sentences that learners can read aloud, small differences that shape meaning remain to be learned. For example, being able to read ‘학교에 가요’ (go to school) and ‘학교에서 공부해요’ (study at school) does not mean knowing what ‘에’ and ‘에서’ do. In the first sentence, ‘에’ marks the school as the destination; in the second, ‘에서’ marks it as the place where studying happens. After learning to read the letters, learners need to understand the relationships that particles attached to words create within a sentence. Korean Basic Dictionary, meaning 3 of ‘에’, meaning 1 of ‘에서’

Separating ‘한’ into its letters, reading ‘옷이’ as [오시] and identifying the destination in ‘학교에 가요’ draw on different kinds of knowledge. Learning the structure of Hangul makes it possible to start reading; studying pronunciation, vocabulary and grammar expands the ability to understand what is read and express it in one's own words. Studying Korean after learning its letters is the process of putting that reading tool to use in actual speech and sentences.