You also need to consider other factors that might make a language especially difficult for YOU, those factors can determine how hard or easy you will be able to learn the next language. Make your choice of what's the hardest language to learn after reading through this article, you can also comment.Arabic, Cantonese, Japanese are said to be the hardest, based on the approximate learning expectations compiled by the Foreign Service Institute (FSI) of the US Department of State. Finnish, Hungarian, and Estonian are also among the hardest because of the countless noun cases. The Pronunciation is even harder than in Asian languages as they usually have long tong twisting consonants. However the list doesn't stop there.
This is a list of the 10 candidates, with an explanation why they made it to this list. If you think other languages should be included too, please comment at the bottom.
1. Chinese: Many factors make Chinese very difficult to learn. For example the characters (Hanzi) used in the writing system seem to be archaic and obscure. Every word is a different symbol and it's not phonetic so it gives you no clues as to how it is pronounced. The tone system also is a pain because Mandarin has four tones. One other reason is, Mandarin has a large number of homophones. For example, the pronunciation "shì" is associated with over thirty distinct morphemes. Some people try to learn this language for that specific reason, being difficult and different.
2. Arabic: The first challenge is the script. Most of the letters have four different forms, depending on where they stand in the word, also vowels are not included when writing. The sounds are tough, but the words are tougher. An English-speaking student learning a European language will run across many familiar-looking words, but English-speaking Arabic students are not so lucky. Arabic is a VSO language, which means the verb usually comes before the subject and object. It has a dual number, so nouns and verbs must be learned in singular, dual, and plural. A present-tense verb has thirteen forms. There are three noun cases and two genders. The other problem is dialects. Arabic spoken in Morocco is as different from Arabic spoken in Egypt and from Modern Standard as French is from Spanish and Latin.
3. Tuyuca: a language of the eastern Amazon. Tuyuca has a sound system with simple consonants and a few nasal vowels, so is not as hard to speak. However it is heavily agglutinating. For example one word, "hóabãsiriga" means "I do not know how to write". It has two words for "we", inclusive and exclusive. The noun classes (genders) in Tuyuca’s language family (including close relatives) have been estimated at between fifty and 140. Most fascinating is that Tuyuca requires verb-endings on statements to show how the speaker knows something. “Diga ape-wi” means that "the boy played soccer (I know because I saw him)". English can provide such information, but for Tuyuca that is an obligatory ending on the verb. Evidential languages force speakers to think hard about how they learned what they say they know.
4. Hungarian: First of all, Hungarian has 35 cases or noun forms. That fact alone makes it a candidate in this list. Hungarian is full of very expressive, idiomatic words, and suffixes. The high amount of vowels and their deep-in-the throat sound makes it very hard to speak as well. It takes more effort to learn it and maintain what you learned then most other languages.
5. Japanese: One main reason why Japanese is so hard is that the written code is different from the spoken code. Therefore, you can't learn to speak the language by learning to read it, and vice versa. What's more, there are three different writing systems to master. The kanji system uses characters borrowed from Chinese. Students need to learn 2,000 to 3,000 of these characters through rote memorization; there are no mnemonic devices to help. Written Japanese also makes use of two syllabary systems: katakana for loan words and emphasis, and hiragana for spelling suffixes and grammatical particles. The State Department allows its students three times as long to learn Japanese as it does languages like Spanish or French.
6. Navajo: This fascinating language can be the most difficult as well. During World War II, the language was used as a code in the Pacific War by bilingual Navajo code talkers to send secure military messages over radio. This had the advantage of being an extremely fast method of encrypted communication. The code was never broken by the Japanese, who were mystified by the sounds they intercepted. Navajo was not chosen as a code language only because it is very hard but also because there was no published grammar or dictionary of the language and because native speakers were readily available. Nearly everything that a language must do is done differently by Navajo than by English. For example in English, we only mark one person on the verb – third person singular, present tense (I read --> he reads) with a suffix. Navajo marks all of the persons with a prefix on the verb.
7. Estonian: This language makes the list too. Estonian has a very rigid case system. "Case" is a grammatical system under which words inflect based on their grammatical function in a sentence. There are twelve cases in Estonian, more than two times the number of cases that exist in most Slavic languages. Apart from the fact that Estonian has many cases, this language is also hard because it has many exceptions in grammar rules, also, many words mean several different things.
8. Basque is also up on top based on a study made by the British Foreign Office. The Basque language has 24 cases. It is impossible to link Basque with any Indo-European language. Basque is probably the oldest known spoken language in Europe. Basque is called an agglutinative language, meaning it likes to use suffixes, prefixes and infixes, so new words are frequently formed by adding a common tag onto the end or the beginning or in the middle of a simpler word. Basque is synthetic, rather than analytic. In other words, Basque uses case endings to denote relationships between words. Basque doesn't just change the end of the verb, it changes the beginning too. In addition to the Indo-European languages moods, Basque also has a few more moods (ex. the potential) and, finally, Basque has a complex system of denoting subject, direct object and indirect object - all of which are crammed into the verb itself.
9. Polish: This language has seven cases and Polish grammar has more exception than rules. German for example has four cases all of which are logical. Polish cases however seem to need more time and effort to learn the logical pattern (if any) or rules; you might have to learn the entire language. Polish has seven cases and Polish grammar has more exception than rules. German for example has four cases all which are logical, Polish cases seem to have no pattern or rules; you have to learn the entire language. Furthermore Polish people rarely hear foreigners speak their language, so with no accent or regional variation, pronunciation must be exact or they will have no idea what you are talking about.
10. Icelandic is a very hard language to learn because of its archaic vocabulary and complex grammar. Icelandic kept all the old noun declension and verb conjugations. Many Icelandic phonemes don't have exact English equivalents. The only way you can learn them is by listening to recordings or to native speakers.
But here is something you should know. The more different a language is from your own (in terms of characters, grammar...), the harder it might seem to you to learn it. One more element should be considered in deciding which language is the most difficult: whether a language follows a logical pattern in its grammar, for example, in English, there is a general rule for creating plurals, adding "s" or "es". In Arabic on the other hand, the plural is irregular most of the time and non-native students spend much of their time learning how to use it.
Finally, one thing is certain, no matter how hard a language is, you really need three things that are essential for learning it: adequate and appropriate learning resources, understanding of the way you learn, and passion of learning.