Signified and signifier are core of semiotics

Considered to be the father of linguistics, Ferdinand de Saussure dedicated his life's work to the focus upon meaning being established through language being considered an interrelated system of elements. Ferdinand de Saussure defines that the linguistic sign is both the combination of a concept (signified) and a sound-image (signifier). The signified is sensory, in which it is not the material sound of actually hearing the word, rather the psychological imprint of the sound. The signifier or sound-image indicates the signified or concept. The signifier cannot be simply called a word because the signified (the concept behind the word) and the signifier are inextricably linked to each other, as the sound-image carries the concept, as a means to bring it into the community of speakers.

The signifier and signified, whilst superficially simple, form a core element of semiotics.

Saussure's ideas are contrary to Plato's notion of ideas being eternally stable. Plato saw ideas as the root concept that was implemented in individual instances. A signifier without signified has no meaning, and the signified changes with person and context. For Saussure, even the root concept is malleable. 

Saussure distinguishes the two principles of the linguistic sign: The Arbitrary Nature of the Sign and The Linear Nature of the Sign. The Arbitrary Nature of the Sign roughly that every means of expression used in society is based on collective behavior or convention, in that the rules of linguistic sign are fixed and not upon the intrinsic value of the sign. Saussure notes that the use of the word arbitrary means that the word symbol or signifier has no natural connection with the concept or signified. Principle II, The Linear Nature of the Sign, states that the signifier- being auditory- is unfolded solely in time (linear time), and the act of signifier has no duality, but only different oppositions to what precedes and what follows.

Following the fundamental definitions of Saussure’s rhetorical case, he writes of the immutability of the sign. The immutability of the sign refers to that the signifier is fixed, not free, rather than the common misconception that individuals can “choose” whichever word we want. The two antithetical forces bond together to form a phenomenon: that freedom of choice and tradition create arbitrary convention, in which “because the sign is arbitrary it follows no other law than that of tradition, and because it is based on tradition, it is arbitrary.”

Following, Saussure acknowledges that while time insures the continuity of language (immutability); time also wields the more or less rapid change of linguistic signs, which is mutability. In the equation of change, tradition or “the old substance” predominate, so the only relative in the equation is change. Change is a shift or loosening in the relationship between the signified and the signifier. Basically, just like all things, time changes language, evolving with the community of speakers. Thus, continuity implies change and the two forces are intrinsic in the formation of langue.

With this knowledge, we can understand that language is the only human institution unlimited in the ways to associate an idea to a sequence of sounds. Yet, language is a product of both social forces and time. Hypothetically, without a community of speakers, a language would sit unchanged for centuries in some immortal person’s lonely brain. In contrast, all current language is based upon something inherited from prior generations. Basically, time works in finite and infinite ways