I'm going to be 'that guy'. The one who takes the question too literally.

I think the difficulty of a language is more related to the resources available than to the intrinsic qualities of the language. With that in mind, I think the most difficult language, of all those that you could theoretically learn, must be Sentinelese.

<a href="https://en.wikipedia.org/wiki/Sentinelese_language" rel="noopener noreferrer" target="_blank">https://en.wikipedia.org/wiki/Sentinelese_language</a>;

<a href="https://en.wikipedia.org/wiki/Sentinelese" rel="noopener noreferrer" target="_blank">https://en.wikipedia.org/wiki/Sentinelese</a>;

No resources exist for learning the Sentinelese language except for the living speakers themselves, all of whom are extremely hostile to outsiders. It's against Indian law to travel near their island. Those people who try to contact the Sentinelese anyway just get shot at with bows and arrows. There have even been some deaths because of this.

Theoretically, you might be able to get close to the Sentinelese and somehow persuade them to accommodate you and teach you their language. But it would be illegal and stupidly dangerous to try.

Actually, the FSI lists Japanese as the hardest. I can't find the original FSI list, but these seem to show that:

<a href="https://www.atlasandboots.com/foreign-service-institute-language-difficulty/" rel="noopener noreferrer" target="_blank">https://www.atlasandboots.com/foreign-service-institute-language-difficulty/</a>;

<a href="https://effectivelanguagelearning.com/language-guide/language-difficulty/" rel="noopener noreferrer" target="_blank">https://effectivelanguagelearning.com/language-guide/language-difficulty/</a>;

I'm learning Japanese and Chinese, and I definitely agree that Japanese is substantially harder. IMO the only thing that's harder about Chinese than Japanese is the tone system: Mandarin has 4 tones (or 5, including the neutral tone.) Tones, and learning the writing system, prove to be the hardest part of learning Mandarin for most English speakers. Cantonese has a lot more tones, somewhere around 8 depending on the source you check and the dialect in question.

Other than the tones, Japanese is harder in almost every aspect. It has a complex stress system called pitch accent, which can be somewhat compared to a tonal system, where words mean different things if you put stress in the wrong places. Mandarin grammar is incredibly similar to English, and Japanese is very different. Japanese uses 3 different writing systems, and the Chinese logography is one of them, so that certainly isn't easier. Not only do you have to know the thousands of characters, but in Japanese (unlike Mandarin), they are read differently depending on context. Japanese also has a much more complex formal/informal speech hierarchy, affecting the ways the verbs conjugate. In Mandarin, there isn't even any conjugation in the first place.

For me, Tagalog was a good bit harder than Mandarin for its grammar, which leads me to believe the FSI also included the writing systems. I really don't think Mandarin is that hard for any reason except tones and its writing system.

However, if you ask me, the answer is probably Navajo, or some other hyper-polysynthetic language which they didn't include in their study :)

mchontz10,

I agree, especially about Tagalog (Filipino). I am a native speaker of English and Tagalog but I don't dare teach Tagalog because it's so complicated that it's hard to tell the rules in grammar, verb conjugation, etc. Plus the complexity of the mixture of English, Spanish, Indian, Malay words in Tagalog makes it even harder to teach. We use three different languages for numbers depending on the context-- Spanish numbers for time, English/Spanish numbers for the amount of money, Tagalog numbers for everything else.

I have studied four languages: French, Japanese, Thai, and currently Spanish. I think Japanese has a reputation for being difficult, but it really is not for the following reasons:

1) It is not tonal like Thai or Chinese. If you are speaking regular standard Japanese and especially if you are female, you can make a flat intonation and it will sound fine.

2) Because the Japanese like to be more indirect than we in the US are, there are a lot of redundancies and hesitations when they speak. This gives you more time to concentrate on understanding the key content words. And when speaking, if you add a lot of those redundant little words, you will sound as if you are more fluent than you actually are!

3) The pronunciation is quite regular, with consonants paired with vowels as with Spanish. One of the only hard sounds for us Americans is their letter "r" and the dipthong "Ryo" or "kyo" as in Tokyo which most Americans say wrong (note: I'm not sure if I used the word dipthong correctly -- what I mean is two sounds sliding together)

4) Granted, the writing is complicated because of the Chinese kanji that they mix with their alphabet; but the alphabet is easy to learn and it is actually fun to learn the kanji -- it is like drawing -- and since they are based on pictures that combine with each other, they are not too difficult to remember.

So please if you are interested in Japanese culture, do not be afraid to learn the language. It is not as difficult as people say it is!

It's always something very individual. For example for me it could be Icelandic or any other Scandinavian language. :-)