Linguists have identified a number of "universals," features found in every language (though most of them are conditional: "any language that has foo will also have bar," which doesn't mean a large percentage of languages will have foo). But are they universal? We have nothing to compare human languages to, after all. Of course, if one includes any or all of these universals in one's definition of "language," you will indeed find that every language has them. Indeed, that's why "language" should be defined based on characteristics — perhaps, "a symbolic system deliberately generated by sentient beings, capable of conveying information and used for that purpose, and regarded by those generating it as a language." The question arises, then, exactly how alien can an alien language get? If it's used by Starfish Aliens it may even require anatomical structures humans don't get — but that doesn't mean it won't have those universals. Even the strangest Starfish Language may well be more normal than we think.