What does atmos mean?
"Atmos" is an informal shortening of the word "atmosphere," most often used conversationally to describe the mood or ambience of a place — a café, a bar, a concert might be said to have a great atmos. It also serves as spoken shorthand in technical fields such as diving and engineering, where it denotes a unit of pressure: one atmos is one standard atmosphere, equivalent to 101,325 pascals, roughly the air pressure at sea level. The word derives ultimately from the Greek "atmos," meaning vapour or steam, the same root that gave English "atmosphere." Because it is a casual clipping, atmos belongs firmly to informal registers — you would rarely encounter it in formal prose, where the full word "atmosphere" is preferred. Its brevity makes it popular in speech, journalism, and social media, lending a breezy, colloquial tone to descriptions of places and events.
nounAn informal shortening of "atmosphere," used both as a casual term for the mood or ambience of a place and as a technical shorthand for a standard atmosphere, the unit of pressure equal to 101,325 pascals.
- An informal shortening of "atmosphere," meaning the mood or ambience of a place.
- A unit of pressure equal to one standard atmosphere (101,325 pascals), used informally in engineering and diving contexts.
"The little café has a lovely atmos in the evenings."
"The pub's cosy atmos made us stay for another round."
"The tank was pressurised to two atmos before the descent."
Rarely pluralised; when referring to multiple units of pressure, speakers more commonly say "atms" or spell out "atmospheres."
"The chamber can withstand pressures of several atmos."
One "atmos" of pressure is exactly what the entire weight of Earth's air presses down on you with at sea level — about a kilogram on every square centimetre.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of atmos
The word traces back to the ancient Greek "atmos," meaning vapour or vaporous air. This root was combined in the 17th century to form "atmosphere," which English then clipped in everyday speech to yield "atmos." The same Greek root underlies related terms such as "atmospheric."
How atmos is actually used
"Atmos" as a clipped form of "atmosphere" is distinctly informal and conversational; in formal writing, use the full word. In scientific contexts it appears mainly as spoken shorthand among divers, engineers, and meteorologists rather than in formal publications.
Easily confused with atmos
"Atmos" is simply an informal clipping of "atmosphere," so it carries a casual register while "atmosphere" remains the full, standard form.
Despite the similar spelling, an atom is the basic unit of a chemical element, whereas atmos refers to atmosphere or a unit of pressure.