relative humidity: meaning, definition, pronunciation and examples
Intermediate (B2)Formal, Scientific, Technical, Everyday (in weather contexts)
Quick answer
What does “relative humidity” mean?
The amount of water vapour present in air expressed as a percentage of the amount needed for saturation at the same temperature.
Audio
Pronunciation
Definition
Meaning and Definition
The amount of water vapour present in air expressed as a percentage of the amount needed for saturation at the same temperature.
A key measure in climatology, meteorology, and HVAC (heating, ventilation, and air conditioning) that indicates the current air moisture level relative to its maximum capacity, which changes with temperature.
Dialectal Variation
British vs American Usage
Differences
No significant difference in meaning or usage. The term is standard in both scientific and lay contexts.
Connotations
Neutral technical term in both. In everyday conversation, it is associated with comfort/discomfort (sticky vs. dry air) and weather forecasts.
Frequency
Equally frequent in technical and weather-related discourse in both varieties.
Grammar
How to Use “relative humidity” in a Sentence
The relative humidity is [adjective, e.g., high].We need to measure the relative humidity.Relative humidity [verb, e.g., affects] comfort.Vocabulary
Collocations
Examples
Examples of “relative humidity” in a Sentence
verb
British English
- The system is designed to relative-humidity control the room. (Note: highly technical/rare use as a compound verb)
American English
- The controller will relative-humidity regulate the greenhouse. (Note: highly technical/rare use as a compound verb)
adjective
British English
- The relative-humidity reading was displayed on the screen. (attributive noun use)
American English
- Check the relative-humidity sensor. (attributive noun use)
Usage
Meaning in Context
Business
Discussed in agriculture, manufacturing (e.g., textile, wood), and building management for product quality and worker comfort.
Academic
A fundamental concept in meteorology, climatology, environmental science, and engineering.
Everyday
Used in weather forecasts and conversations about personal comfort, drying clothes, or houseplants.
Technical
Precisely defined and measured with hygrometers; critical in HVAC design, museum conservation, and data centre management.
Vocabulary
Synonyms of “relative humidity”
Strong
Neutral
Weak
Vocabulary
Antonyms of “relative humidity”
Watch out
Common Mistakes When Using “relative humidity”
- Using 'humidity' alone to mean 'relative humidity' in technical contexts. 'Humidity' can be ambiguous (could mean absolute or relative).
- Saying 'percent' after a number without stating 'relative humidity' (e.g., 'It's at 80 percent' is clear only in context).
FAQ
Frequently Asked Questions
Absolute humidity is the actual mass of water vapour in a given volume of air (e.g., grams per cubic metre). Relative humidity is the ratio of the current absolute humidity to the maximum possible absolute humidity at that temperature, expressed as a percentage.
It changes primarily because air temperature changes. In the morning when it's cool, the air is closer to its saturation point (higher RH). As the day warms up, the air's capacity to hold moisture increases, so the relative humidity decreases if no extra moisture is added.
Not necessarily. 100% relative humidity means the air is saturated with water vapour. This can cause fog, mist, or dew. Rain requires the additional process of water droplets coalescing and becoming heavy enough to fall from clouds.
For human health and comfort, and to prevent mould growth, indoor relative humidity is generally recommended to be between 30% and 60%, with 40-50% often considered ideal.
The amount of water vapour present in air expressed as a percentage of the amount needed for saturation at the same temperature.
Relative humidity is usually formal, scientific, technical, everyday (in weather contexts) in register.
Relative humidity: in British English it is pronounced /ˌrel.ə.tɪv hjuːˈmɪd.ə.ti/, and in American English it is pronounced /ˌrel.ə.t̬ɪv hjuːˈmɪd.ə.t̬i/. Tap the audio buttons above to hear it.
Phrases
Idioms & Phrases
- “It's not the heat, it's the humidity. (common saying about discomfort)”
Learning
Memory Aids
Mnemonic
Think: RELATIVE humidity is RELATIVE to temperature. Like a RELATIVE size cup – a hot day is a bigger cup that can hold more water vapour before becoming full (100%).
Conceptual Metaphor
AIR IS A SPONGE / CONTAINER: Relative humidity is how full the sponge is compared to its current maximum capacity.
Practice
Quiz
What does a relative humidity of 50% indicate?