‘艰巨’ is an adjective meaning 'arduous' or 'formidable', describing tasks, challenges, or responsibilities that are extremely difficult, demanding great effort, perseverance, or resources. The character 艰 (jiān) means 'difficult' or 'hard', often implying hardship or struggle, while 巨 (jù) means 'huge' or 'enormous', emphasizing scale and magnitude. Together, they intensify the sense of difficulty—not just hard, but massively so—conveying both qualitative and quantitative weight.

This word is commonly used in formal, written, or serious spoken contexts: government reports, academic discussions, project planning, or personal reflections on major life goals. It rarely appears in casual conversation about everyday minor inconveniences (e.g., not for 'hard to find parking'); instead, it’s reserved for large-scale, long-term, or high-stakes endeavors like national development, scientific breakthroughs, or overcoming systemic social issues.