Ferdinand de Saussure may in many respects be considered the founder of the modern science of language. He too was the first to call for a structural approach to language, i.e., a scientific description of language in terms of relations between units, irrespective of any properties which may be displayed by these units but which are not relevant to the relations or deducible from the relations.
Thus, Saussure would have it that the sounds of a spoken language, or the characters of a written language, should be described, not primarily in terms of phonetics or of graphiology, respectively, but in terms of mutual relations only, and, similarly, the units of the linguistic content (the units of meaning) should be described primarily not in terms of semantics but in terms of mutual relations only.
According to Saussure, it would be erroneous to consider philology as a mere aggregate of physical, physiological, and acoustic descriptions of speech sounds, and of investigations into the meanings of words, and we may add, of psychological interpretations of such sounds and meanings. On the contrary, the real units of language are not sounds, or written characters or meanings: the real units of language are the relata which these sounds, characters, and meanings represent.
The main thing is not the sounds, characters, and meanings as such, but their mutual relations within the chain of speech and within the paradigms of grammar. These relations make up the system of a language, and it is this interior system which is characteristic of one language as opposed. to other languages, whereas the representation by sounds, characters, and meanings is irrelevant to the system and may be changed without affecting the system.
What is a structural approach to language?