* Topping the list is Mandarin, a tonal and pictographic language. Every sound has its 4 unique pronunciations and meanings. * Arabic is the official language in over 20 states. It is written from left to right; most letters have 4 different forms depending on where you place them in a word.  * Japanese has a massive volume of characters to master, only two tenses and three independent writing systems. Thus, it isn't a language you can learn at a whim.  * Hungarian isn't like any other European language. Its grammar rules are tough, the language sounds are challenging, and it relies heavily on idioms to convey its meaning.  * The Korean language loves homonyms, words with the same sounds but different meanings. Its characters can be read from left to right and from top to bottom. Unlike other languages, Korean was invented and did not witness organic growth. Also, the grammar rules are indeed tricky to learn.