What is the difference between the enablement requirement and the utility requirement?

The enablement requirement of 35 U.S.C. 112(a) and the utility requirement of 35 U.S.C. 101 are distinct but related concepts in patent law. The MPEP states:

“The requirement of 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, first paragraph as to how to use the invention is different from the utility requirement of 35 U.S.C. 101. The requirement of 35 U.S.C. 101 is that some specific, substantial, and credible use be set forth for the invention. On the other hand, 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, first paragraph requires an indication of how the use (required by 35 U.S.C. 101) can be carried out, i.e., how the invention can be used.”