Definition of substitution. 1  1a : the act, process, or result of substituting one thing for anotherb : replacement of one mathematical entity by another of equal value. 2  2 : one that is substituted for another.
Homogenized milk is any sort of milk that has been mechanically treated to ensure that it has a smooth, even consistency. The homogenization process typically involves high temperatures, agitation, and filtration, all aimed at breaking down milk's naturally occurring fat molecules.
In summary, half-and-half is equal parts cream and milk. Evaporated milk is regular milk that has had a large portion of its water removed to create a concentrated milk. Half-and-half is slightly higher in calories and fat because of the cream it contains.