Communication scholar and teacher Frank E. X. Dance, offers the following explanation for the difference between communication and communications: 

"Unfortunately, referring to the study of communication*s* is a widespread illiteracy in our field.  Abstract conceptual nouns that
refer to ideas, processes, or conditions cannot be pluralized by adding an "s" or "es."  To attempt to do so, when it does not produce total
nonsense, engages the related concrete morpheme and, while it may appear to make sense, changes the basic meaning.  Consider that those who study radio, television, and press do not necessarily study radios, televisions, and presses; students of journalism are not students of journalisms, scholars engage in scholarship, not scholarships;biologists study life, not lives; medical students study medicine in general, and medicines only occasionally; nutritionists study nutrition, not nutritions; attorneys study justice, not justices; and Tolstoy's book was titled *War and Peace*, fortunately, not *Wars and Peaces*. Theorists of communication may occasionally analyze specific messages, or communications, but that is not the name of their field of study."

Quarterly Journal of Speech, November, 1984, p. 473