Structuralism is a theory of humankind in which all elements of human culture, including literature, are thought to be parts of a system of signs. Critic Robert Scholes has described structuralism as a reaction to "’modernist’ alienation and despair."
European structuralists such as Roman Jakobson, Claude Lévi-Strauss, and Roland Barthes (before his shift toward poststructuralism) attempted to develop a semiology, or semiotics (science of signs). Barthes, among others, sought to recover literature and even language from the isolation in which they had been studied and to show that the laws that govern them govern all signs, from road signs to articles of clothing.
Structuralism was heavily influenced by linguistics, especially by the pioneering work of Ferdinand de Saussure. Particularly useful to structuralists was Saussure’s concept of the phoneme (the smallest basic speech sound or unit of pronunciation) and his idea that phonemes exist in two kinds of relationships: diachronic and synchronic. A phoneme has a diachronic, or "horizontal," relationship with those other phonemes that precede and follow it (as the words appear, left to right, on this page) in a particular usage, utterance, or narrative—what Saussure, a linguist, called parole (French for "word"). A phoneme has a synchronic, or "vertical," relationship with the entire system of language within which individual usages, utterances, or narratives have meaning—what Saussure called langue (French for "tongue," as in "native tongue," meaning language). An means what it means in English because those of us who speak the language are plugged into the same system (think of it as a computer network where different individuals can access the same information in the same way at a given time).
Following Saussure, Lévi-Strauss, an anthropologist, studied hundreds of myths, breaking them into their smallest meaningful units, which he called "mythemes." Removing each from its diachronic relations with other mythemes in a single myth (such as the myth of Oedipus and his mother), he vertically aligned those mythemes that he found to be homologous (structurally correspondent). He then studied the relationships within as well as between vertically aligned columns, in an attempt to understand scientifically, through ratios and proportions, those thoughts and processes that humankind has shared, both at one particular time and across time. Whether Lévi-Strauss was studying the structure of myths or the structure of villages, he looked for recurring, common elements that transcended the differences within and among cultures.
Structuralists followed Saussure in preferring to think about the overriding langue, or language of myth, in which each mytheme and mytheme-constituted myth fits meaningfully, rather than about isolated individual paroles, or narratives. Structuralists also followed Saussure's lead in believing that sign systems must be understood in terms of binary oppositions (a proposition later disputed by poststructuralist Jacques Derrida). In analyzing myths and texts to find basic structures, structuralists found that opposite terms modulate until they are finally resolved or reconciled by some intermediary third term. Thus a structuralist reading of Milton's Paradise Lost (1667) might show that the war between God and the rebellious angels becomes a rift between God and sinful, fallen man, a rift that is healed by the Son of God, the mediating third term.
Although structuralism was largely a European phenomenon in its origin and development, it was influenced by American thinkers as well. Noam Chomsky, for instance, who powerfully influenced structuralism through works such as Reflections on Language (1975), identified and distinguished between "surface structures" and "deep structures" in language and linguistic literatures, including texts.

Adapted from The Bedford Glossary of Critical and Literary Terms by Ross Murfin and Supriya M. Ray. Copyright 1998 by Bedford Books.