When people start thinking about learning a foreign language, one of the first thoughts that spring to mind is “I am not going to learn [insert a language] because it is too hard”. Dismissing a thought of learning a particular language just because it is generally considered hard would be a mistake; there are many other important factors to consider. However, the idea that some languages are harder than others is, unfortunately, correct.
How hard it is to learn a particular foreign language for you depends on many different factors, such as natural talent, available learning resources, and your learning plan, but I believe the single most important factor is how closely related the language is to the languages you already speak.
Since this article is written in English, I will concentrate mainly on difficulty of various languages for English speakers and advantages and disadvantages English speakers have, but many of the ideas apply also to speakers of other languages.
English is a good starting point for Germanic and Romance languages
English vocabulary is a mixture of words coming from Germanic languages, French, Latin, Greek, and a handful of others. As a result, adjectives in English are often not derived from the corresponding nouns but rather from words originating in a different language, for example:
ten – decimal
end – final
There are many others. These are called collateral adjectives, and you can read a long list of such pairs on Wiktionary.
While this feature is not so good for English learners, it is very helpful for English speakers. It will be easy for you to remember that “hand” is Hand in German and mano in Spanish, that “ten” is tien in Dutch and dieci in Italian, or that “end” is Ende in German and fin in French.
In summary, when an English speaker starts learning a Germanic or a Romance language, hundreds or even thousands of words will look familiar to them. Since vocabulary tends to be the nemesis of most language learners, this makes learning a Germanic or a Romance language much easier than learning Slavic and Asian languages.
English grammar and pronunciation cause trouble
Even though English shares a lot of words with other European languages, its grammar is quite different. There are no grammatical genders (inanimate objects being treated as male or female), no noun declensions (we would say “of me”, not “of I”, but nothing changes between “the tree” and “of the tree”), virtually no conjugations (most English verbs have only four different forms, e.g. walk, walks, walked, and walking, while verbs in French can have over 40 different forms!), no endings for adjectives depending on gender, and the list could go on.
This makes it harder for English speakers to understand various common grammatical constructions in other European languages. This may be a problem for some; some people find it hard to accept that things that “are the same” in English must be translated using several different expressions into another language.
Also, almost all European languages, perhaps with the exception of French, sound, in my opinion, similar to some extent. English has a very “non-continental” sound (much more so in American English than in British English, however), and that’s probably the reason why native English speakers learning a European language tend to have a stronger accent than Continental Europeans learning the same language.
English is not so closely related to any other language
Oddly enough, I would say that it’s actually harder for a native English speaker to become a polyglot than for speakers of other European languages. Languages within the major language families present in Europe are usually quite closely related; it is very easy for a Czech to learn Polish or Slovak and for a Spaniard to learn Italian or Portuguese.
The major European language most closely related to English is probably Dutch, but still, Germans will have a much easier time learning Dutch than the British. (Just as a side note: While this seems to be a theoretical explanation of the Great Britain being among the most monolingual countries in Europe, the data shows that Continental Europeans in fact rarely choose to actively learn a language closely related to their mother tongue.)
“So, what languages should I learn?”
I think there exists a “myth” in the English speaking world that Spanish and Italian are “really easy”, but this is not really the case. Spanish and Italian are probably among the easiest languages when you just started learning the language (because of simple pronunciation rules and a lot of familiar vocabulary) but I believe that when you reach the later stages of learning (when you try to attain some level of proficiency), Spanish and Italian grammar can be pretty tricky.
I would say there is not much difference among various Romance and Germanic languages in terms of difficulty of reaching proficiency as a native English speaker. German is traditionally considered somewhat harder than most other Germanic and Romance languages, but the difference is not very significant, in my opinion.
Once we leave the realm of Germanic and Romance languages, things start to get complicated. Slavic languages are much harder to learn than Romance and Germanic languages, and you can read my explanation of the phenomenon in a separate article. If you would like to learn a Slavic language, Slovak may be a good choice. It is slightly easier than most other Slavic languages, has quite a neutral “Slavic sound”, and it is a good starting point for learning other Slavic languages. On the other hand, it has also one of the lowest number of speakers in the Slavic family.
Finnish and Hungarian have very little in common with Slavic languages in terms of grammar and vocabulary, but they are quite similar in terms of ease (or rather hardness) of learning.
Modern Greek is usually grouped with Slavic languages when it comes to rating of difficulty of learning, but I don’t think this is justified. In terms of structure and ease of learning, Greek grammar seems to be very similar to German, and an educated speaker of English should already know a significant number of Greek words. The writing system should also be easy to master, since most English speakers are already familiar with the Greek alphabet to a certain degree.
East Asian languages are a completely separate chapter. My knowledge of these is quite limited, but it’s probably easy to imagine what could go wrong. Chinese grammar is usually considered quite simple, but its pronunciation and writing system are a real pain for Westerners. Japanese has quite European-friendly pronunciation, but its writing system is very complicated. Korean has quite a simple writing system and phonology, but people usually consider it as hard as Chinese or Japanese for some reason (which I don’t know because I’ve never come in contact with it).
Based on the typical experiences of learners of East Asian languages, it seems you should be able to reach fluency in three or four “easy” European languages within the same time frame you can reach fluency in just a single East Asian language, which is something you should take into account when you decide which language to learn.