A small difference in stroke symbolizes a difference in meaning in Chinese characters. Mandarin also contains 4 tones which only differ slightly in pitch and enunciation. There are an abundant number of homophones as well; the same phonetic sound can have a completely different meaning depending on context.
Grammar is one of the major hurdles in learning Arabic. For example, Arabic uses a verb-subject-object format, rather than a subject-verb-object format. There are also three levels of plurality: singular, dual and plural. In script writing, most letters have 4 different forms depending on their location in the word.
A main difficulty in the Polish language is its alphabet; it is comparable to Latin with a few discrepancies. Polish is also an inflection language like Latin, using 7 cases to define noun usage in a sentence. A mark of its difficulty can be seen in its youth; most people do not master Polish until they reach 16.
Similar to other European languages, Hungarian does not distinguish between genders. It is also an agglutinative language, relying heavily on prefixes and suffixes to denote different meanings. Hungarian is also one of the most inflection-heavy languages: nouns can have up to 238 forms depending on inflection.
Finnish is a highly phonological language; word construction rules are determined by how the letter sounds. For example, the vowels are phonetically divided into two classes. The rule states that a word can only contain vowels from one class. A student must also learn how to distinguish sounds in consonants as well. For example, sounds such as "p", "t" and "k" are called stop consonants, which have their own rules of use.
Russian vocabulary is particularly hard because of the many ways words are created. Adding a prefix or suffix to the word makes its meaning completely different. Russian is also notably difficult because of its two pairs of consonants: plain and palatalized. The distinction between the two is made through stressing certain sounds in a word.
Japanese also uses a character system to represent different words. Notably, Japanese has around 10,000 to 15,000 characters, with no clear way to use memorization techniques such as mnemonics. It also has two syllable systems: katakana for placing emphasis and hiragana for grammatical particles.
Estonian has 12 different cases in its grammatical system; a case is when a word inflects based on its use in a sentence. There is also a distinction for "impersonal" subjects -- an undetermined subject -- in Estonian language; there are particular word forms that need to be used when impersonal subjects perform an action.
Icelandic is particularly difficult because it remained mostly archaic; words have generally not evolved to a more modern use. As a result, many Icelandic words cannot be easily translated. Because of this, students learning Icelandic typically have to solely rely on listening to native speakers.
German is highly inflected in both nouns and verbs. For noun inflections, it has 4 different cases and 3 different genders. German also has multiple infinitives, potentially creating long chains of verbs at the end of each sentence. This is because verbs are located at the very end of subordinate clauses; applicable infinitives have to be added to each one.