The document lists and provides brief details about 6 of the hardest languages to learn: Chinese, Arabic, Japanese, Russian, Finnish, and Icelandic. Chinese is described as a tonal language with many homophones. Arabic letters have multiple forms and vowels are often not written. Japanese uses three writing systems and two reading methods. Russian has a complex grammar involving conjugation and cases. Finnish has 15 noun cases and vowel harmony. Icelandic has archaic vocabulary, complex grammar, long words, and unique pronunciations.