Words can be classified into native tongues and naturalized words. The native tongues are our original words that have had its origin in our nation since the early ages like '하나(one)', '둘 (two)', 사람 (human), 땅(earth) while the naturalized words are the borrowed words from the neighbor countries like'버스(bus), 커피(coffee), 컴퓨터(computer). Our nation has borrowed many vocabularies mainly from China, Mongolia and other nations around.

The examples are '붓(brush)', '송골매(duck hawk)' and others. Most of the naturalized words introduced after 21st century come from English language, There are many examples such as '커피(coffee)', 넥타이(necktie)' and '인터넷(Internet)' and many words still keep coming today.

To prevent the spelling disorder, a spelling system for naturalized words were formulated. The very first draft was a draft for unified naturalized words spelling system proposed by Chosun Language Institution in 1939. The current draft was notified first in 1986. The followings are several important rules in the naturalized words spelling system.

Second, the naturalized words should follow the Korean spelling system because they are also the Korean language. Therefore, only seven consonants of 'ㄱ','ㄴ','ㄹ','ㅁ','ㅂ','ㅅ', and 'ㅇ' can be the final consonants in the naturalized words. And, the double vowels such as 'ㅑ','ㅓ','ㅛ' and 'ㅠ' cannot be used after 'ㅈ' and 'ㅊ'. Therefore, '디스켄(diskette)' and '커피숖(coffee shop)' are wrong and they should be revised into '디스켓', and '커피숍'. Neither '레져(leisure)' nor '쥬스(juice)' is right. '레저’ and '주스‘ are the right words.

Third, glottallized sounds are not used in the naturalized words. Therefore, '까스(gas)', '땜(dam)', '뻐스(bus)', '써비스(service)'are the wrong spellings. '가스', ’댐', '버스', ’서비스'are right.