‘艰深’ is an adjective meaning 'profoundly difficult'—typically describing texts, concepts, theories, or subjects that demand considerable intellectual effort and background knowledge to understand. The first character 艰 (jiān) means 'arduous' or 'hard to accomplish', while the second character 深 (shēn) means 'deep', suggesting depth of content, abstraction, or complexity. Together, they emphasize both the strenuous effort required and the profound, layered nature of what is being described.

This word is commonly used in academic, scholarly, or technical contexts—especially when referring to classical philosophy, advanced mathematics, dense literary criticism, or highly specialized scientific literature. It carries a neutral-to-formal register and is rarely used for everyday challenges like physical labor or simple tasks. While it implies difficulty, it does not suggest impossibility; rather, it signals that mastery requires sustained study and expertise.