There are different accepted Romanizations of Hangul. One is McCune-Reischauer which was designed in the 1930s and used until 2000. In 2000 the Revised Romanization or Ministry of Culture romanization was put into effect by South Korea. There are also some other ones (like the Yale version used by linguists) but those are the main two. For example: standard MR writes hangul as "han'gǔl” and the RR version is “han-geul” or “hangeul”.

Because it is pronounced 'u' But the correct way is 'eo' but if someone read that not knowing it they might actually pronounce it 'eo' I prefer it when people use 'eo' it just seems more correct And sometimes when I see 'u' I think it is 우 not 어 I think it is just a matter of preference but I think writing it as 'eo' is more correct :)

Actually eonni is the right way of spelling and pronounciation you are not exactly saying 'u', but 'eo'...you just need to practice pronounciation of the invidual 'letters'. With hyeong its the same. I believe Koreans pronounciate this word with 'yeo' sound rather than 'u'. As some of the korean letters are quite similar and hard to distinguish, it is understandable that you got confused. However, you are right. There are some irregularities in words such as 'mat' which means taste The word itself is pronounces 'mat', but when you add 'isso' to it, the sound changes to 'mashisso' (it means delicious) At first, it may seem difficult, but with practice youll be fine Keep up the good work and hope this is the answer you are looking for^^