These nouns denote that which is perceived through the nose by means of the olfactory sense. Smell is the most general word, including all the rest, and odour is its closest synonym. These two words are often used interchangeably, and both may be applied to pleasant, unpleasant or neutral sensations. But odour is the more nearly neutral word, being freer of connotations than smell and better suited to scientific contexts. Odour tends to take its character from the words that qualify it: a pungent odour ; a foul odour . Smell has a character of its own ?a simple, hearty, forthright quality better suited to the kitchen than to the laboratory: cooking smells . Odour may sometimes signify a more delicately pleasing perception than smell : the clean smell of soap; the spicy odour of incense. And whereas a smell may sometimes be a blend of separate emanations, an odour is more commonly traceable to a single source: the smell of the sick room; the odour of formaldehyde.

An aroma is an odour both pleasing and distinctive, such as that given off by an appetizing food as it cooks or by good pipe tobacco as it burns. An aroma may be savoury or smoky, permeating the air, or it may be delicate or spicy; but it is always stimulating to the senses: the aroma of fresh coffee. Bouquet is applied primarily to the delicate aroma that distinguishes a fine wine: He lifted the wine glass and sniffed the bouquet appreciatively.

A scent is any odour , natural or artificial, that is or may be faintly diffused through the air. A scent is always delicate and often pleasing: the scent of a sachet. Perfume is the same as scent except that it has more elegance, and so is synonymous with fragrance , which is a sweeter, fresher, more pervasive scent : the lingering fragrance of lilacs. Scent , perfume and fragrance are the words properly applied to dusting powder and other toiletries. Smell and odour seem inelegant and inappropriate in such contexts, except when smell is used with simple sincerity, as by a child: He liked the smell of his mother’s talcum powder.

Applied to the natural emanations of human beings, smell and odour often signify something unpleasant or offensive, though the words are not limited in this way: the smell of sweat; body odour. Fragrance is used only of women and often occurs in popular writing, connoting a fresh, clean smell : the fragrance of her hair. Scent denotes the characteristic odour of an animal ?a faint residual odour that lingers along the ground over which the animal has passed. A natural human odour is referred to as a scent only when the person in question is being tracked down like an animal: Bloodhounds followed the scent of the escaped prisoner. Scent and smell may also denote the olfactory sense itself; but scent is usually reserved for animals, especially dogs, and suggests an unusually sharp sense of smell : the keen scent of the foxhound.

Stink and stench are strong words and are applied to foul, offensive odours and smells that make a person hold his nose or that turn him sick to the stomach. Of the two, stink suggests a sharper sensation; stench , a more sickening one: the stink of sweaty feet; the stench of gangrene. Both words apply to what is rotting or decaying, but stench denotes the stronger and more overpowering odour : the stench of a battlefield after a slaughter.

Bouquet and stench , being the most specific of these words, are seldom used figuratively. But odour , stink and smell are often so used.

• There was an odour of fear in the air; He made quite a stink about it; It had the smell of foul play.