emulsion

/ɪˈmʌlʃɪn/

/ɪˈmʌlʃən/

Other forms: emulsions

Ever notice the separate layers of oil and vinegar in salad dressing? Give the bottle a shake and those layers combine in a process called emulsion or the combination of liquids that don't dissolve into each other.

Emulsion comes from the Latin mulgere meaning to "milk out." Seems strange, doesn't it? But in the early seventeenth century, the term was used to describe the milky liquid that result from crushing almonds in water. Think of natural peanut butter and how it separates with a thick layer of oil on top. When you stir it with a long spoon, that's the process of emulsion, or a combination of two liquids that don't dissolve into each other.

Definitions of emulsion

1. noun

   (chemistry) a colloid in which both phases are liquids
   “an oil-in-water emulsion”

   type of:

   colloid

   a mixture with properties between those of a solution and fine suspension
2. noun

   a light-sensitive coating on paper or film; consists of fine grains of silver bromide suspended in a gelatin
   synonyms: photographic emulsion

   type of:

   coat, coating

   a thin layer covering something