e·mul·sion

(ĭ-mŭl'shən)

n.
  1. A suspension of small globules of one liquid in a second liquid with which the first will not mix: an emulsion of oil in vinegar.
  2. A photosensitive coating, usually of silver halide grains in a thin gelatin layer, on photographic film, paper, or glass.
[New Latin ēmulsiō, ēmulsiōn-, from Latin ēmulsus, past participle of ēmulgēre, to milk out : ē-, ex-, ex- + mulgēre, to milk; see melg- in Indo-European roots.]

The American Heritage® Dictionary of the English Language, Fourth Edition