from
The Collaborative International Dictionary of English v.0.48
Casein \Ca"se*in\, n. [Cf. F. cas['e]ine, fr. L. caseur cheese.
Cf. {Cheese}.] (Physiol. Chem.)
A proteid substance present in both the animal and the
vegetable kingdom. In the animal kingdom it is chiefly found
in milk, and constitutes the main part of the curd separated
by rennet; in the vegetable kingdom it is found more or less
abundantly in the seeds of leguminous plants. Its reactions
resemble those of alkali albumin. [Written also {caseine}.]