Is water vapour the same as steam?

Not exactly. Steam is water vapor at a high temperature, often associated with boiling. The white 'cloud' from a kettle is mostly tiny liquid water droplets formed when the invisible water vapour cools slightly.

Can we see water vapour?

No, pure water vapour is invisible. What we often call 'steam' or 'mist' is visible because it consists of millions of tiny liquid water droplets that have condensed from the vapour.

What's the difference between 'humidity' and 'water vapour'?

Water vapour is the substance itself (gaseous H₂O). Humidity is a measure of how much water vapour is present in the air, usually expressed as a percentage (relative humidity).

Why is water vapour important for the climate?

Water vapour is the most significant greenhouse gas. It traps heat in the atmosphere and is a key component in cloud formation and precipitation, playing a central role in Earth's weather and climate systems.

water vapour

Medium

UK/ˈwɔːtə ˌveɪpə/US/ˈwɔːt̬ɚ ˌveɪpɚ/

Formal, Scientific, Technical

My Flashcards

Definition

Meaning

Water in its gaseous state, especially when mixed with air.

The invisible, gaseous phase of water that is present in the atmosphere and is a key component of humidity, clouds, and the water cycle.

Linguistics

Semantic Notes

Refers specifically to the gaseous state, not tiny liquid droplets (mist, steam). Implies a component of a mixture (e.g., with air).

Dialectal Variation

British vs American Usage

Differences

Spelling: 'vapour' (UK) vs. 'vapor' (US). No significant difference in meaning or usage.

Connotations

Identical scientific/technical connotations in both varieties.

Frequency

Slightly more frequent in UK English due to spelling preference, but term usage is identical.

Vocabulary

Collocations

strong

atmospheric water vapoursaturated with water vapourwater vapour contentcondenses into water vapour

medium

amount of water vapourrelease water vapourinvisible water vapourwater vapour pressure

weak

clouds of water vapourmeasure water vapourrising water vapour

Grammar

Valency Patterns

The [noun] contains/absorbs/releases water vapour.Water vapour [verb: condenses/forms/rises].

Vocabulary

Synonyms

Strong

H₂O(g)gaseous water

Neutral

water vaporatmospheric moisturehumidity

Weak

steamdampness

Vocabulary

Antonyms

iceliquid watersolid water

Phrases

Idioms & Phrases

“No common idioms. Sometimes used in metaphorical phrases like 'evaporate into water vapour' meaning to disappear completely.”

Usage

Context Usage

Business

Rare, except in specific industries like HVAC, construction, or meteorology.

Academic

Common in physics, chemistry, geography, meteorology, and environmental science texts.

Everyday

Used in explanations of weather (humidity, clouds, dew) and household phenomena (kettle steam, bathroom condensation).

Technical

Precise term in engineering, climatology, and thermodynamics.

Examples

By Part of Speech

verb

British English

The hot pavement will quickly vapourise the puddle.
The process vapourises the water.

American English

The hot pavement will quickly vaporize the puddle.
The process vaporizes the water.

adverb

British English

Not applicable/rare.

American English

Not applicable/rare.

adjective

British English

The vapour pressure was measured.
A vapour barrier was installed.

American English

The vapor pressure was measured.
A vapor barrier was installed.

Examples

By CEFR Level

The sun heats the water and makes water vapour.
You can see your breath on a cold day because it has water vapour.

Clouds form when water vapour in the air cools and condenses.
The amount of water vapour in the air is called humidity.

Scientists measure water vapour concentration to predict weather patterns.
The greenhouse effect is intensified by increased atmospheric water vapour.

Satellite data allow for the precise global mapping of tropospheric water vapour.
The latent heat released during the phase change from water vapour to liquid is a major driver of storm systems.

Learning

Memory Aids

Mnemonic

Think of a boiling kettle: the invisible gas leaving the spout is WATER VAPOUR; the white 'steam' you see a few centimetres out is actually tiny liquid droplets condensed from it.

Conceptual Metaphor

Often framed as a TRANSPORTABLE AGENT (water vapour rises, is carried, condenses) or a MEASURABLE COMPONENT (content, level, pressure of water vapour).

Watch out

Common Pitfalls

Translation Traps (for Russian speakers)

Avoid confusing with 'пар' (par) when it refers to steam (hot vapor with visible droplets). 'Water vapour' is more specific and scientific.
Do not translate as 'водяной пар' in every context; in everyday talk about steam from food, 'steam' is more natural.

Common Mistakes

Using 'steam' as a direct synonym (steam is hot water vapor, often with visible droplets).
Confusing water vapour with mist or fog (which are liquid).
Omitting the space: 'watervapour' is incorrect.

Practice

Quiz

Fill in the gap

When the air cools, the condenses to form dew on the grass.

Multiple Choice

Which of the following is the most accurate definition of 'water vapour'?

FAQ

Frequently Asked Questions

: Not exactly. Steam is water vapor at a high temperature, often associated with boiling. The white 'cloud' from a kettle is mostly tiny liquid water droplets formed when the invisible water vapour cools slightly.
: No, pure water vapour is invisible. What we often call 'steam' or 'mist' is visible because it consists of millions of tiny liquid water droplets that have condensed from the vapour.
: Water vapour is the substance itself (gaseous H₂O). Humidity is a measure of how much water vapour is present in the air, usually expressed as a percentage (relative humidity).
: Water vapour is the most significant greenhouse gas. It traps heat in the atmosphere and is a key component in cloud formation and precipitation, playing a central role in Earth's weather and climate systems.