A look at the Korean from the perspective of an English speaker trying to learn the language. The truth is that Korean is one of the hardest languages on Earth for an English speaker to learn.
Most agree that Korean is a hard language to learn.
The alphabet, Hangul at least is reasonable; in fact, it is elegant. But there are four different Romanizations – Lukoff, Yale, Horne, and McCune-Reischauer – which is preposterous. It’s best to just blow off the Romanizations and dive straight into Hangul. This way you can learn a Romanization later, and you won’t mess up your Hangul with spelling errors, as can occur if you go from Romanization to Hangul. Hangul can be learned very quickly, but learning to read Korean books and newspapers fast is another matter altogether because you really need to know the hanja or Chinese character that is in back of the Hangul symbols.
Bizarrely, there are two different numeral sets used, but one is derived from Chinese so it should be familiar to Chinese, Japanese or Thai speakers who use similar or identical systems.
Korean has a wealth of homonyms, and this is one of the tricky aspects of the language. Any given combination of a couple of characters can have multiple meanings. Japanese has a similar problem with homonyms, but at least with Japanese you have the benefit of kanji to help you tell the homonyms apart. With Korean Hangul, you get no such advantage.
Similarly, there seem to be many ways to say the same thing in Korean. The learner will feel when people are using all of these different ways of saying the same thing that they are actually saying something different each time, but that is not the case.
One problem is that the b, p, j, ch, t and d are pronounced differently than their English counterparts. The consonants, the pachim system and the morphing consonants at the end of the word that slide into the next word make Korean harder to pronounce than any major European language. Korean has a similar problem with Japanese, that is, if you mess up one vowel in sentence, you render it incomprehensible.
The vocabulary is very difficult for an English speaker who does not have knowledge of either Japanese or Chinese. On the other hand, Japanese or Chinese will help you a lot with Korean. Chinese and Japanese speakers can usually learn Korean quickly.
Korean is agglutinative and has a subject-topic discourse structure, and the logic of these systems is difficult for English speakers to understand.
Meanwhile, Korean has an honorific system that is even wackier than that of Japanese. However, the younger generation is not using the honorifics so much, and a foreigner isn’t expected to know the honorific system anyway.
Maybe 60% of the words are based on Chinese words, but unfortunately, much of this Chinese-based vocabulary intersects with Japanese versions of Chinese words in a confusing way.
Speakers of Korean can learn Japanese fairly easily. Korean seems to be a more difficult language to learn than Japanese. There are maybe twice as many particles as in Japanese, the grammar is dramatically more difficult and the verbs are quite a bit harder. The phonemic inventory in Korean is also larger and includes such oddities as double consonants.
Korean is rated by language professors as being one of the hardest languages to learn.
Korean is rated 5, hardest of all.