‘毒性’ (dú xìng) is a noun meaning ‘toxicity’—the degree to which a substance can harm living organisms. It combines 毒 (dú), meaning ‘poison’ or ‘toxin’, and 性 (xìng), a suffix meaning ‘nature’ or ‘property’. Together, they literally mean ‘the nature/property of being poisonous’. This word is commonly used in medical, scientific, and environmental contexts—for example, when discussing drug safety, pesticide effects, or pollution risks.

Unlike the standalone character 毒, which can refer to poison, drugs, or even metaphorical harm (e.g., 毒品 ‘narcotics’), 毒性 specifically denotes the measurable biological effect of a toxic agent. It often appears with modifiers like 高 (gāo, ‘high’), 低 (dī, ‘low’), or 无 (wú, ‘none’) to indicate severity: e.g., 高毒性 means ‘highly toxic’. It’s rarely used in casual speech but frequently appears in warnings, research reports, and public health information.