毫秒 (háo miǎo) is a unit of time equal to one-thousandth of a second (0.001 seconds). It combines two characters: 毫 (háo), meaning 'a tiny amount' or 'one-thousandth', and 秒 (miǎo), meaning 'second'. Together, they literally mean 'a thousandth part of a second'. This term is widely used in scientific, technical, and computing contexts—such as measuring response times, network latency, or camera shutter speeds.

In everyday Chinese, 毫秒 appears less frequently than seconds or minutes but is common in precise timing discussions—like sports timing systems, software performance testing, or electronics specifications. It’s not used in casual conversation about daily schedules; instead, it belongs to formal or technical registers where precision matters. The character 毫 is also found in other metric prefixes (e.g., 毫米 háo mǐ 'millimeter'), reinforcing its role as a standard prefix for 10⁻³.