繁重 (fánzhòng) is an adjective meaning 'heavy' or 'demanding', especially when describing workloads, responsibilities, or tasks that require significant time, energy, or mental effort. The character 繁 (fán) means 'complex', 'numerous', or 'busy', while 重 (zhòng) means 'heavy' or 'weighty' — together, they convey the sense of something being both voluminous and burdensome. It’s commonly used in formal or semi-formal contexts, such as workplace discussions, academic settings, or official reports.

This word emphasizes not just physical weight but psychological or logistical pressure — for example, a tight deadline with many interdependent tasks. Unlike simple synonyms like 多 (duō, 'many') or 忙 (máng, 'busy'), 繁重 implies sustained strain and seriousness. It rarely describes objects literally (e.g., you wouldn’t say 繁重的箱子), but rather abstract loads: duties, schedules, studies, or administrative work.