But in contrast to the "Haerye" account, the non-stops "ng" , ㄴ "n" , ㅁ "m" , and ㅅ "s" were derived by "removing" the top stroke or strokes of the basic letters. (No letter was derived from ㄹ "l" .) This clears up a few points that had been problematic in the "Haerye." For example, while it is straightforward to derive ㅁ "m" from ㅂ "b" by removing the top of ㅂ "b" in Ledyard's account, it is not clear how one would derive ㅂ "b" by adding something to ㅁ "m", since ㅂ "b" is not analogous to the other stops: If ㅂ "b" were derived as in the "Haerye" account, it would be expected to have a horizontal top stroke similar to those of ㄱ "g" , ㄷ "d" , and ㅈ "j" . In order to maintain the Chinese convention of initial and rime, Sejong and his ministers needed a null symbol to refer to the lack of a consonant with an initial vowel. He chose the circle ㅇ with the subsequent derivation of the glottal stop ㆆ "ʼ" , by adding a vertical top stroke by analogy with the other stops, and the aspirate ㅎ "h" , parallel the account in the "Haerye." (Perhaps the reason he created a new letter rather than adopting one from ʼPhags-pa was that it was awkward to write these Chinese initials in ʼPhags-pa, where ㅇ and ㆆ were both written as digraphs beginning with "y," ꡭꡝ and ꡗꡖ.) However, Ledyard's explanation of the letter ㆁ "ng" differs from the "Haerye" account; he sees it as a fusion of velar ㄱ "g" and null ㅇ, reflecting its variable pronunciation. The Korean alphabet was designed not just to write Korean, but to accurately represent Chinese. Many Chinese words historically began with , but by Sejong's day this had been lost in many regions of China, and was silent when these words were borrowed into Korean, so that only remained at the middle and end of Korean words.