vapor

[ vey-per ]

noun

1. a visible exhalation, such as fog, mist, steam, smoke, or noxious gas, diffused through or suspended in the air:

   The vapors rising from the bogs smelled muddy.

2. Physics. a gas at a temperature below its critical temperature.
3. a substance converted into a gaseous state for technical or medicinal uses.
4. a combination of gaseous particles of a substance and air.
5. vapors, Archaic.
   1. harmful exhalations formerly supposed to be produced within the body, especially in the stomach.
   2. mental or physical illness, such as depression or hypochondria, formerly supposed to result from such exhalations, especially in women.
6. the vapors. Often Facetious. a feeling of being overwhelmed with strong emotion:

   That guy gives the press the vapors every time he announces a new project.

7. Archaic.
   1. a strange, senseless, or fantastic notion.
   2. something insubstantial or transitory.

verb (used with object)

1. to cause to rise or pass off in, or as if in, vapor; vaporize.
2. Archaic. to affect with the vapors; depress.

verb (used without object)

1. to rise or pass off in the form of vapor.
2. to emit vapor or exhalations.
3. to talk or act grandiloquently, pompously, or boastfully; bluster.

vapor

/ ˈveɪpə /

noun

1. the US spelling of vapour

vapor

/ vā′pər /

1. The gaseous state of a substance that is normally liquid or solid at room temperature, such as water that has evaporated into the air.
2. See more at vapor pressureSee also water vapor
3. A faintly visible suspension of fine particles of matter in the air, as mist, fumes, or smoke.
4. A mixture of fine droplets of a substance and air, as the fuel mixture of an internal-combustion engine.

Other Words From

• va·por·a·ble adjective
• va·por·a·bil·i·ty [vey-per-, uh, -, bil, -i-tee], noun
• va·por·er noun
• va·por·less adjective
• va·por·like adjective

Word History and Origins

Origin of vapor¹

First recorded in 1325–75; Middle English vapour, from Latin vapor “steam,” of uncertain origin; akin to vapidus vapid ( def ) and vappa “wine that has gone flat”; perhaps cognate with Greek kapnós “smoke” ( acapnia ( def ) )

Usage

The words vapor and steam usually call to mind a fine mist, such as that in the jet of water droplets near the spout of a boiling teakettle or in a bathroom after a shower. Vapor and steam, however, refer to the gaseous state of a substance. The fumes that arise when volatile substances such as alcohol and gasoline evaporate, for example, are vapors. The visible stream of water droplets rushing out of a teakettle spout is not steam. As the gaseous state of water heated past its boiling point, steam is invisible. Usually, there is a space of an inch or two between the spout and the beginning of the stream of droplets. This space contains steam. The steam loses its heat to the surrounding air, then falls below the boiling point and condenses in the air as water droplets. All liquids and solids give off vapors consisting of molecules that have evaporated from the substance. In a closed system, the vapor pressure of these molecules reaches an equilibrium at which the substance evaporates from the liquid (or solid) and recondenses on it in equal amounts.

Example Sentences

Higher temperatures enhance the atmosphere’s capacity to hold water vapor, increasing the quantities of moisture evaporating off the landscape.

From Los Angeles Times

Additionally, the increase in CO2 allows more vapor to form in the air.

From Salon

Perhaps most notably, it has a very low mass — 10% the mass of Jupiter despite being 80% its volume, with an atmosphere of water vapor, methane, carbon dioxide, carbon monoxide and ammonia.

From Salon

Authorities ordered the evacuation of approximately 150 homes in a Ventura neighborhood Sunday because of “potentially dangerous levels of hydrocarbon vapors” and placed another 2,600 homes under a warning to possibly leave.

From Los Angeles Times

Water vapor is the only emission generated from the propulsion system.

From Los Angeles Times

Related Words

• condensation
• fog
• gas
• moisture
• smog
• smoke
• steam