"Nature of the Linguistic Sign" by Ferdinand de Saussure
From RhetorClick
In “Nature of the Linguistic Sign,” Ferdinand de Saussure argues that a linguistic sign can be broken up into two parts: a concept (signified) and a sound-image (signifier). He points out how the sign is arbitrary and not based on an inherent relationship between the signified and signifier. He says the sign is both immutable—no one in a community can alter the language at will—and mutable—given enough time, social forces will cause shifts in language, though language is always inherited from the preceding period.