The purpose of the article is to delimit and relate the entities mentioned in the title. Each of them is discussed, with focus on languages or linguistic systems. Languages should be distinguished from their conventional use (usage) and its product: texts and the utterances they consist of, as well as from the users’ language faculty and competence. Especially the relation between languages and usage, utterances, and competence is discussed. The author argues for a consistently usage-based view of languages, which is incompatible with mentalism, as usage and texts consist of physical units like sounds or letters. The conclusion is that languages are social products: institutions, more precisely sign systems comprising the units of expression. Utterances are the maximal sign and define the actual language. The article discusses if languages are «multimodal» or independent of expression, and concludes that they are not. Spoken, written and gestural languages are different types of sign systems.