October 9 was Hangul Day, a day celebrating the invention of the Korean alphabet. All writing systems are cool, but the Korean alphabet is a special favourite of linguists because the symbols are designed based on the phonetic features of their sounds. For example, from Wikipedia:
ㄱ g [k], ㅋ k [kʰ]
Basic shape: ㄱ is a side view of the back of the tongue raised toward the velum (soft palate). (For illustration, access the external link below.) ㅋ is derived from ㄱ with a stroke for the burst of aspiration.
ㄴ n [n], ㄷ d [t], ㅌ t [tʰ], ㄹ r [ɾ, l]
Basic shape: ㄴ is a side view of the tip of the tongue raised toward the alveolar ridge (gum ridge). The letters derived from ㄴ are pronounced with the same basic articulation. The line topping ㄷ represents firm contact with the roof of the mouth. The middle stroke of ㅌ represents the burst of aspiration. The top of ㄹ represents a flap of the tongue.
As this video from the late linguist Jim McCawley points out, this means that King Sejong and his scholars had a very modern understanding of articulatory phonetics and the phonology of Korean way back in the 1400s, and a sense of how important it was to design a system that was easy to learn so that everyone could be literate.
The individual sounds are then combined into syllable blocks. For example, here’s the word “hangul” itself:
For more information, Wikipedia is a good place to start, and there’s also a video series about learning Hangul.