As nouns the difference between rotation and alternate
is that
rotation is rotation while
alternate is that which alternates with something else; vicissitude.
As an adjective alternate is
being or succeeding by turns; one following the other in succession of time or place; by turns first one and then the other; hence, reciprocal.
As a verb alternate is
to perform by turns, or in succession; to cause to succeed by turns; to interchange regularly.