复杂 (fù zá) is an adjective meaning 'complex' or 'complicated'—describing something with many interconnected parts, difficult to understand or handle. The character 复 (fù) originally means 'to repeat', 'to return', or 'multiple layers'; 杂 (zá) means 'mixed', 'varied', or 'miscellaneous'. Together, they convey the idea of layered multiplicity—things that are not simple or straightforward but involve overlapping elements, ambiguity, or intricacy.

This word is commonly used in academic, technical, and everyday contexts—for example, when describing systems, relationships, instructions, or emotions. It often implies a contrast with 简单 (jiǎn dān, 'simple') and appears in phrases like 复杂的问题 (a complex problem), 复杂的结构 (a complex structure), or 复杂的心情 (a complicated/emotionally layered mood). It can carry a slightly neutral-to-negative connotation, suggesting difficulty or challenge rather than mere richness.