What does 難題 mean?
難題 is a Japanese noun meaning “difficult problem; challenge” in English. It is written as 難題 in kanji, なんだい in hiragana, and nandai in romaji. This word is part of JLPT N1 vocabulary.
Example sentence
君はそれらの難題に対処しなくてはならない。
You have to cope with those difficult problems.