odore

Odor is the perceptual experience of a volatile chemical substance that stimulates the olfactory system. An odor arises when odorant molecules reach the nasal cavity and bind to receptors on olfactory sensory neurons. The brain interprets patterns of receptor activation as a smell, producing a wide range of experiences from pleasant to unpleasant. Odor perception is inherently subjective and can be influenced by context, attention, prior exposure, and cultural background.

Odorants vary in chemical structure and volatility, and many odors result from mixtures of multiple compounds. Some odors are well known by name, such as geosmin (earthy), vanillin (vanilla), or skatole (pungent), illustrating the diversity of odor notes. The sense of smell, or olfaction, operates alongside taste to form flavor perception and plays roles in food identification, safety, and social communication.

Measurement and study of odors involve sensory evaluation and standards for threshold detection. Concepts such as odor thresholds quantify the lowest concentration perceivable by humans, while odor units or odor activity values relate concentration to threshold. Olfactory adaptation and cross-adaptation describe changes in sensitivity after exposure to odors.

Sources of odors span natural and human-made environments. Natural odors come from plants, soils, foods, and animals; anthropogenic odors emanate from wastewater treatment, agriculture, and industrial processes. Odor control relies on containment, ventilation, and treatment technologies such as adsorption (activated carbon), biofiltration, or thermal oxidation.

Etymology traces the word to Latin odor, with modern English spellings distinct across varieties (odor in American English, odour in British English; in Italian, odore denotes smell).