«O великий, могучий, правдивый и свободный русский язык!»
Russian is what they speak in Russia.
It has the interesting characteristic of being able to convey very complex meanings in short sentences, but to make natural, cheerful or positive statements quite intractable, such as «с удовольствием» to mean "gladly", "with pleasure", or «самый лучший» for "best", as well as important ones requiring concision, such as «Будьте внимательны» for "be careful".
It is very poetic, with declinations and conjugation allowing for many beautiful rhymes ending in a, in e or ef, in i or iye, in o or of or even more exotic things like ik or ak (and still others, ending in m, s).
Another difficulty is the shuffling of letters of lookalike words to form different meanings, sometimes directly opposite (e.g., выключить and включить), or deviations from one letter, such as здание (building), задание (task). Dislexic Russians must have a hell of a time! This, on the other hand, also power up the language for poetic constructs.
Russian grammar is notoriously difficult, so we discuss it on its own page, as well as Russian words and concepts or idioms.