Hungarian

Hungarian's ancestors arrived in the Carpathian basin around 895 CE from somewhere east — possibly the Volga-Ural region. The Magyar people, speaking a Uralic language, settled in what's now Hungary among Slavic, Germanic, and Romance speakers but kept their language. The result, a thousand years later, is a Uralic linguistic island in the middle of Indo-European Europe, with no close relatives among neighbouring languages.

Around eighteen, depending on how you count — Hungarian uses cases for many of the spatial relationships English handles with prepositions ('into the house', 'out of the house', 'onto the house', 'off the house', 'at the house', 'from the house' all become different case suffixes on the noun). The number of cases makes Hungarian look intimidating, but the system is regular and the case suffixes attach predictably according to vowel harmony.

Hungarian verbs come in two conjugation patterns depending on whether the object of the verb is definite (a specific known thing) or indefinite (a non-specific or unstated object). 'I see (something)' and 'I see it/the thing' use different verb endings. The system is grammatical rather than lexical and propagates throughout verb forms across the language.

Distantly — both are Uralic, but in different branches. Hungarian is Ugric; Finnish is Finnic. They share grammatical features (vowel harmony, agglutinative morphology, no grammatical gender, rich case systems) and a small core of cognate words from common Uralic roots, but their daily vocabulary is largely independent. Speakers of one need study to follow the other.

Among the harder major European languages. Eighteen cases, vowel harmony, agglutinative morphology, definite/indefinite conjugation, and a vocabulary with virtually no English cognates outside recent loans all add up to a steep curve. Hungarian compensates with very regular grammar — almost no irregularities — and a phonemic spelling system. Most learners describe Hungarian as challenging but rewarding.