There are many models of the linguistic sign (see also sign (semiotics)). A classic model is the one by the Swiss linguist Ferdinand de Saussure. According to him, language is made up of signs and every sign has two sides (like a coin or a sheet of paper, both sides of which are inseparable):

the signifier (French signifiant), the "shape" of a word, its phonic component, i.e. the sequence of graphemes (letters), e.g., <"c">-<"a">-<"t">, or phonemes (speech sounds), e.g. /kæt/