Which is the hardest language to learn?

The US Foreign Service Institute, which trains American diplomats, groups languages by how long English speakers need to reach professional working ability. Its hardest group, Category IV, includes Arabic, Mandarin, Cantonese, Japanese and Korean, which take about 88 weeks or 2,200 class hours. By contrast, languages close to English such as Spanish, French, Italian and Dutch need only about 24 to 30 weeks. Mandarin is tough because it uses thousands of characters and four tones that change meaning, while Japanese mixes three writing systems. Difficulty is always relative, though: for a Chinese speaker, Japanese characters are far easier than they are for an English speaker.