Most Difficult Languages - Polish
I've read about the supposed difficulty of many languages. Some I don't know at all (like Chinese or Arabic, which I'd imagine are difficult), but I did have the opportunity to learn one of the hardest, and supposedly the most grammatically-complex Slavic language, Polish. It is certainly harder than Croatian--another Slavic language--which I already knew when I started to learn Polish.
Here's one (somewhat trivial, but illustrative) example of the relative complexity of languages: the number 2.
English, Spanish, Dutch: 1 form (two, dos, twee)
Portuguese: 2 forms (dois/duas) - depending on gender (2 - masculine & feminine)
Croatian: 7 forms (dva, dvije, dvoje, dvojica, dvojice, dvojici, dvojicu) - depending on gender (3 - masculine, feminine, and neuter) and case in one specific form. There were other variants historically but they're not used anymore.
Polish: 17 forms. Depends on gender (3), case for all forms. Pretty much all these forms occur in regular speech (6-11 less often than the others)
17 grammatical forms for the number 2
- dwóch (or dwu)
- dwom (or dwóm)
Why is Polish so complex?
Poland's history is one of being attacked and subjugated by its neighbors throughout most of its history, either by Germans, Austrians, Swedes or Russians. Many times the speaking of Polish was forbidden, so people were understandably protective of their language and less likely to have foreign intrusion into it. (English readily absorbs foreign words because American, Brits, Australians, etc don't feel like their language is threatened.) Also, "world languages" simplify much more rapidly, while "niche languages" don't have the same sort of pressure.
Even the names of months, which are usually similar in all the languages of the world, retain old Slavonic forms in Polish:
- January - styczeń (from the Polish word for joining, since January joins two years together)
- February - luty (from the Polish word for freezing cold; this is the only month that is grammatically an adjective, not a noun)
- March - marzec (from Mars - the 3rd month is the Roman god Mars's month, as it is in English)
- April - kwiecień (from the Polish word for flower, since this is the month when flowers bloom)
- May - maj (the only one adopted from the Roman calendar)
- June - czerwiec (from the Polish word for reddening...named after the Polish cochineal, a red insect that is used for red dye and is harvested in June - thanks, Lola!)
- July - lipiec (from the Polish word for linden tree, which blooms in July in Poland)
- August - sierpień (from the Polish for for sickle, since this is the month of harvest)
- September - wrzesień (from the Polish word for heather, which turns a brilliant shade of purple then)
- October - październik (from the Polish word for a type of flax mulch used in the fields during this month)
- November - listopad (almost literally - falling leaves)
- December - grudzień (from the Polish word for hardened, frozen ground)
Imperfect and Perfect Verbs in Polish
Another grammatical difficulty is the concept of imperfect and perfect verbs in Polish (and other Slavic languages). The verb "to see" has two completely different verbs in Polish: widzieć and zobaczyć. The only difference is that you use the first if something happens continuously or more than once, and the second if it only happens once.
Widziałem - I saw (repeatedly in the past, like I saw the sun come up every morning)
Zobaczyłem - I saw (only once; I saw the sun come up yesterday)
This is not a tense difference - the verbs themselves are different.
There are many other examples:
to take - brać / wziąć
I took - Brałem (repeatedly), wziąłem (only once)
to sigh - wzdychać / westchnąć
I sighed - wzdychałem (repeatedly), westchnąłem
So for every verb in English, you effectively have to learn two verbs in Polish, which often conjugate in the future tense completely differently from each other (the past tense is usually the same, which makes for relatively easy side-by-side comparisons, like above). The present tense is impossible for the perfective verb because you can not be doing something now and finish it at the same time.
For about 5% of Polish verbs, there is no perfective version, so you luckily only have to learn one verb counterpart.
Plural forms change based on number
The last major wrinkle is that the plural form of nouns changes depending on the number. In English, there is only one plural form for the word "telephone" and that's "telephones", whether you have just 2 or 100. In Polish, it's 2, 3 or 4 "telefony" and 5 "telefonów". (Grammatically speaking, 2, 3 and 4 take the nominative case, while 5 and beyond take the genitive case)
Occasionally the difference between the nominative and genitive forms makes the jump between 4 and 5 awkward sounding.
4 or 5 hands: 4 ręce (rent-seh) but 5 rąk (ronk)