impurity
n. C / U B2 Upper Intermediate US //ˌɪmˈpjʊɹəti// UK //ɪmpjˈʊɹɪti// im·pu·ri·ty
n. a small amount of something that is not pure. It can be a dirt particle in water or a bad quality in a person's character.
n. a substance that is not pure; an element or compound that is present in a material in an undesired or unintended state. Often used metaphorically to describe a flaw in a person's character or a process.
The water was clear, but it still contained a small impurity.
The chemist used a special filter to remove any impurity from the liquid before the final test.
While the diamond was nearly flawless, a microscopic impurity in the crystal lattice caused it to refract light in a slightly different way than a pure specimen.
From impure + -ity. From Middle French impurité, from Latin impuritas.