Contrary to popular beliefs, Japanese is easy. The tricky part is reading and writing but that's because of all the Kanjis, the third Japanese writing system. Arabic and Russian aren't hard either, but one has to practice them daily before mastering them. I'm Lebanese so Arabic is one of my native languages (Alongside French and English) although I stopped Arabic because I wanted to learn Spanish instead. Anyway,  we shouldn't count the minor languages because they are too hard for anyone to learn. You have to grow into them or else you can't understand a word they're saying, like the Inuits for example. Out of the famous languages, I think Thai is the most complicated language to learn. It has a lot of similar sounds (About 60 ways to say Cai I think). Traditional Chinese is very very hard as well but not impossible, many people are learning Chinese (and Japanese) nowadays. Russian isn't easy but it isn't very hard either. My Tennis Teacher learned Russian on his own (his wife is Russian).

I guess it's all relative. I mean Spanish is harder for an American or a Russian than it is for a French or Italian. It's been a year since I started Spanish and I can already understand most of the time, I still have trouble creating sentences but just another year would do it. Similarly, Japanese is hard for a westerner than it is for a Chinese. Not because they are similar (except for the Kanjis, which litteraly mean Chinese Characters) but because they have more similarities than with Western languages.

I speak and write 3 languages (Arabic, French and English). I understand Spanish and little of Japanese, I'm currently learning both languages.
I plan on learning Mandarin Chinese, Italian, Sign Languages and maybe Latin as well (I love languages), which me good luck.

Joey Ayoub

Surely this depends on your native language.  Obviously, French is easy enough to learn for English speakers, whereas it is just as hard as English for a Chinese speaker.

Anonymous

“I speak English, Swedish and Finnish. The last one is the most difficult for me without any doubt. But it depends on what makes the language in question difficult to different people. For me, Finnish is tough because of its vocabulary that doesn´t resemble anything I have known so far. Just learning the most basic words has been taking me like forever. Swedish on the other hand has been a breeze.

”

I share many of your views in that for some languages with a complicated grammar are easy  -  or at least easier than other languages  -  whereas some others find languages with hardly any grammar a breeze. There are also those who see no particular difference in the difficulty. I remember my school days and some students who never learned the conjugation of German adjectives. Some never learned to pronounce English understandably. A friend of mine who had great difficulty with English pronunciation nevertheless acquired a large enough vocabulary to be able to read a few dozen scientific books in English. He needed that to pass his exams at Helsinki University.

If I hadn't seen that myself, I would never have believed it was possible! He had nothing and no one to support him! He couldn't hear anyone pronounce the words the way he pronounced them anywhere! Yet his vocabulary consisted of thousands of words! His achievement convinced me that as far as a language is concerned, nothing is impossible.

As for natives not knowing the grammar of their own language, Finns are an excellent example. Educated news reporters make mistakes with seemingly simple things like the comparison of adjectives almost every day on television and radio. Mind you, the difference between a plural comparative and a plural superlative can be reversing two letters in the middle of a six-syllable adjective, but I still think anyone with an academic education should get it right.

Another thing they never learn is ordinals. I think one Finn out of ten would be able to say correctly "I'm telling you for the 638th time." Most don't even try! All of the three digits (6, 3 and 8) have to be inflected correctly.

I wish you a lot of success in your efforts to learn Finnish!

CB