NOTE: The following is an undergraduate essay; it is not particularly rigorous and did not receive a particularly high mark when submitted. If you are really interested in Semiotics, I recommend checking other online resources such as Semiotics for Beginners
— Mark Pursey
Rather than looking at language as a set of names for things, or even as a set of words with meanings, Saussure's structuralism considers language as a multitude of signs, where each sign links a phonic sound (the signifier) with an idea (the signified). Whereas the notion of naming things implies a finite number of well defined objects and concepts requiring labels, Saussure's linguistic sign acts as a two-way link between the sound (or more specifically the sound image - the "psychological imprint" of a sound) and the idea. It is bi-directional in the sense that just as the word "red" may evoke notions of red objects, a notion of something red may elicit the sound image "red". A sound is meaningless if it is not so linked to an idea, and likewise for an idea to be coherent one requires the capacity to articulate it.
Structuralism recognises neither ideas nor sounds as having intrinsic or absolute value; both realms are considered as indeterminate and continuous. Just as the notion of "large" has no inherent value, without recognition of at least one other size notion, eg "small", value is perceived only in terms of difference in relation to other ideas and sound. For example, if large were the only size notion, to describe something as "large" or "not large" would be meaningless, (unless the signifier "not-large" is understood as signifying smallness, thus giving us a second size notion). Introducing a third size notion of "tiny" to our idea space alters somewhat the boundaries of large and small, reducing their scope and the distance between them, effectively narrowing their meanings. Similarly, language sounds, or sound images, are perceived largely in terms of their differences from other sounds. For example, an English word spoken at two different frequencies (or two different speeds), is generally perceived as the same word, even though the sounds are clearly different.
The linguistic sign therefore serves to link not points but regions of sound-space and idea-space, the boundaries of which are determined by the existence of other sounds and other ideas. This is to say that a sign taken on its own, without reference to a larger system of such signs, can have no meaning.
The pairing of sound with idea is considered by Saussure almost entirely arbitrary, determined purely by convention within a linguistic community. This is to say there is nothing in the sound itself that links it to an idea, nor is there anything in the idea which links it to a particular sound. That human languages can differ so much in sound (and to a lesser extent in the ideas which can be signified) is powerful support for this assertion.
If we accept that the bond between the signifier and the signified is arbitrary, and therefore that the sign itself is arbitrary, then the chief concern of structuralism becomes the analysis of value, which in turn requires the analysis of the system as a whole, in keeping with the aforementioned relational nature of both sound and idea.
For such analysis to be feasible, Saussure perceived that serious reductions needed to be made. To this end he performed a series of bifurcations on language. After eliminating nonverbal systems (Saussure denigrates writing as derivative of speech-a sign of a sign), he splits verbal language into two components, la langue, the underlying system of conventions which exists in the collective mind of the linguistic community, and la parole, the actual speaking of the language. Saussure's parole is effectively an instantiation of la langue, as substance is to form, and hence considered external. Though relevant, the external is not deemed essential to an understanding of the structure of la langue.
Since language is constantly changing, in both intelligible (langue) and sensible (parole) form, it is difficult to examine as a system, so la langue is further split into two parts: the synchronic, a linguistic system existing at a particular point in time, and the diachronic, a collection of linguistic elements changing over time. The synchronic can be seen as something of a snapshot, or a cross section of la langue as sliced across the time axis, whereas the diachronic may be imagined as a slice along the time axis, revealing the trajectory of individual elements of la langue as they develop and change. With an aim to examining signs within a self contained system, Saussure's structuralism focuses on the synchronic.
The synchronic system can then be described in terms of two axes: the paradigmatic and the syntagmatic. The paradigmatic is concerned with meaning based on association, and the syntagmatic is based on combination. To elaborate: the paradigmatic is concerned with the 'fixed' value of signs based on their immediate associations with other signs (like the association of the sound/idea "large" with other size notions such as "small", as well as with other sound images, such as "barge"). On the other hand, the syntagmatic is concerned with the 'dynamic', pertaining to meaning conferred by the combination, order and sequence of signs (such as the sequence, or syntagm: "That is a very large bird"-The idea signified by the sound image "bird" is modified by the words preceding it).
The relationship between the paradigmatic and the syntagmatic is analogous to that between the synchronic and diachronic, in that the former is like a snapshot of related values, where the latter offers a trajectory where value is related to the sequence or progression. The paradigmatic is structuralism's primary concern, being more readily systematisable, although a consideration of both (and the correlations between them) is essential for any structuralist analysis.