alphabet, and then whittled down to a minimal set of basic letters through featural derivation, so that a more convenient shape from among the Phagspa letters could be used as the basis for the hangul letters for the sibilants .) The basic hangul letters have been simplified graphically, retaining the essential shape of Phagspa but with a reduced number of strokes. For example, the box inside Phagspa g is not found in hangul ㄱ [k]. This simplification allowed for complex clusters, but also left room for an additional stroke to derive the aspirate plosives, ㅋㅌㅍㅊ. On the other hand, the non-plosives, nasals ng (see below) ㄴㅁ and the fricative ㅅ, were derived by removing the top of the tenuis letter. (No letters were derived from ㄹ.) This clears up a few points. For example, it is easy to derive ㅁ from ㅂ by removing the top of ㅂ, but it is not clear how one would get ㅂ by adding something to ㅁ, since ㅂ is not analogous to the other plosives: if they were derived, as in the traditional account, we'd expect them all to have a similar vertical top stroke. Sejong also needed a null symbol to refer to the lack of a consonant, and he chose the circle, ㅇ. The subsequent derivation of the glottal stop ㆆ, by adding a vertical top stroke by analogy with the other plosives, and the aspirate ㅎ parallel the account in the Hunmin Jeong-eum. The phonetic theory inherent in this derivation is more accurate than modern IPA usage. In the IPA, the glottal consonants are posited as having a specific "glottal" place of articulation. However, recent phonetic theory has come to view the glottal stop and [h] to be isolated features of 'stop' and 'aspiration' without a true place of articulation, just as their hangul representations based on the null symbol assume. The ng is the odd letter out here, as it is in the Hunmin Jeong-eum. This may reflect its variable behavior. Hangul was designed not just to write Korean, but to accurately represent Chinese. Besides the letters covered here, there were quite a few more used to represent Chinese etymology. Now, many Chinese words began with ng, at least historically, and this was being lost in several regions of China by Sejong's day: that is, etymological ng was either silent or pronounced in China, and was silent when borrowed