Intimate mixture of oil and water, generally of a milky or cloudy appearance. Emulsions may be of two types: oil-in water (where water is the continuous phase) and water-in-oil (where water is the discontinuous phase).
An emulsion may look like a single liquid, but it’s made up of particles of one liquid distributed throughout another liquid. For example, if oil and water is emulsified, it forms an emulsion in which small droplets of oil are suspended in the water, but the two liquids aren’t fully blended together (as they would be if stirred together water and vinegar, for example).
In technical chemistry terms, an emulsion is a colloidal suspension in which the substances mixed together are both liquids. Both colloids and suspensions involve particles of one substance distributed in another without being dissolved.