What does emulsion mean?
An emulsion is a mixture of two liquids that would ordinarily separate — most famously oil and water — in which tiny droplets of one liquid remain evenly suspended throughout the other. Familiar examples include mayonnaise, milk, butter, and many cosmetics and medicines. Because such mixtures are naturally unstable, they typically need help from an emulsifier, a substance such as egg yolk or mustard that keeps the droplets from coalescing; without it, an emulsion eventually splits back into its components. The word has important specialist uses: photographers speak of the light-sensitive emulsion coating film, and in British English 'emulsion' commonly denotes a type of flat, water-based wall paint. Derived forms include the verb 'to emulsify' and the agent noun 'emulsifier'. Scientifically versatile and everyday at once, 'emulsion' bridges the kitchen, the laboratory, and the paint aisle, making it a genuinely useful word to know.
nounA mixture of two liquids that do not normally dissolve in each other, in which droplets of one liquid are dispersed throughout the other, such as oil in water. In photography, it also refers to a light-sensitive coating on film or paper.
- A mixture of two immiscible liquids in which one is dispersed as fine droplets through the other.
- A light-sensitive chemical coating used on photographic film or paper.
- (British English) A type of water-based paint, short for 'emulsion paint'.
"Mayonnaise is a classic emulsion of oil and vinegar held together by egg yolk."
"Whisking the dressing vigorously creates a temporary emulsion of oil and lemon juice."
"Old black-and-white photographs rely on a silver halide emulsion coated onto the film."
Regular plural, used when discussing multiple mixtures or varieties.
"Chemists study how different surfactants stabilise emulsions."
The word 'emulsion' comes from the Latin for 'milking out' — because milk was the first emulsion humans ever noticed.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of emulsion
Emulsion derives from the Latin verb 'emulgere', meaning 'to milk out', formed from 'ex-' ('out') plus 'mulgere' ('to milk'), the same root behind English 'emollient' via a related sense of softening. It entered English around the early 17th century, initially referring to milky medicinal extracts. Its modern scientific sense of one liquid dispersed in another developed later, and it shares its Latin dairy-root lineage with words like 'emulsify'.
Related word forms
How emulsion is actually used
Common in scientific and culinary contexts. In British English, 'emulsion' alone often refers to matte interior wall paint.
Easily confused with emulsion
In an emulsion two liquids are mixed with one dispersed in the other, whereas in a suspension solid particles float in a liquid.