Usus is the common usage of linguistic units in a particular speech community. It may be used as one of the criteria of laying out prescriptive norms for standard language usage.
Usus can be contrasted with both low-frequency usage and codified standard usage. The term is used to designate usage that has widespread or significant acceptance among speakers of a language, regardless of its conformity to the sanctioned standard language norms.
Usus was a crucial term in the research of Danish linguists Otto Jespersen and Louis Hjelmslev.