Odor

An odor, or odour, is a sensory impression produced when volatile chemical compounds, known as odorants, interact with the olfactory system in the nasal cavity. Odorants bind to receptors on olfactory neurons, triggering signals that are processed by the brain as a smell. Odors can arise from single compounds or complex mixtures, and their perception depends on concentration, temperature, humidity, and the presence of other odors.

Sensitivity to odorants varies among individuals due to genetic differences in olfactory receptors. Some people may be unable to detect certain odors, a condition known as specific anosmia. Odors are commonly described by qualitative categories such as fruity, floral, earthy, chemical, or foul, and they contribute to the perception of flavor through retronasal olfaction.

In practice, odor assessment is used in food, beverage, and environmental industries for quality control and regulatory purposes. Sensory analysis with trained panels remains a primary method for evaluating odor, complemented by instrumental techniques like gas chromatography–mass spectrometry to identify volatile compounds, though the perceived odor can be influenced by context and individual variation.

Odor thresholds indicate the minimum concentration at which an odorant is detectable, while odor intensity describes the strength of the perceived smell. Adaptation can occur with repeated exposure, reducing sensitivity. Environmental odors can originate from natural processes such as decay or from human activities including industry and agriculture, influencing both hygiene and quality considerations.