‘臭氧’ (chòu yǎng) is a chemical compound composed of three oxygen atoms (O₃). The character 臭 means 'smell' or 'stink', referring to ozone’s sharp, pungent odor—often noticeable after lightning strikes or near electrical equipment. 氧 means 'oxygen', indicating its elemental composition. Though the first character suggests something unpleasant, ozone is not inherently harmful: in the upper atmosphere (the ozone layer), it protects Earth from harmful ultraviolet radiation.

In ground-level air, however, ozone is a major component of smog and can irritate the respiratory system, especially for people with asthma or other lung conditions. It’s commonly discussed in environmental science, public health advisories, and weather reports—particularly during hot, sunny days when pollution reacts with sunlight to form ozone. Scientists monitor ozone concentrations closely, and governments issue air quality alerts when levels become hazardous.