Oxford English Dictionary Term n. 13a. A word or phrase used in a definite or precise sense in some particular subject, as a science or art; a technical expression.
13b. In wider application: Any word or group of words expressing a notion or conception, or denoting an object of thought; an expression (for something).
Literary and cultural terms are essential elements of literary study, but in contrast to other intellectual fields, esp. science and technology, literary terms often morph quickly, adapting their meanings to changing circumstances—like most language. (Such changes are also true for scientific and technological terms, but because they refer to natural objects or forces,
Different terms bump into, shade into, or turn into each other.
How literary terms may shift meanings or applications:
1. More than one term may apply to a single textual phenomenon.
In discussing literary genres, a text like Jane Eyre may be a novel, a gothic romance, a women's text.
A Sherlock Holmes story is a short story, a detective story, a mystery, an example of late Victorian or Edwardian literature.
All these terms (and more) are true descriptions, so even if you've learned a text one way, you can't be surprised at hearing it described the other way, or other ways.
Literature remains meaningful by being as specific as possible without reducing meaning to one simple answer. Instead, the best analyses or answers open to further analysis and meaning.
2. A single term may shift meanings and applications in different contexts.
For popular culture romance means a love story, but as a literary genre, romance means a type of story like a quest, escape, revenge, rescue, etc. These two types of romance are not mutually exclusive, but in different contexts the same term serves different meanings.
Rationale for literature's shifting terminology:
If literature is great, we don't run out of ways to talk about it. Terms multiply their meanings as our knowledge grows. Which term matters or what the term means at any given moment depends on what you're talking about and why.
Tech-sorts, engineers, or bottom-line financial thinkers lose patience with such multiplicity and flexibility of meanings, but human society talks and works this way. Shades of meaning associated with words evolve, grow, or drop away as our culture evolves. To adapt to an ever-growing and -changing world, literary studies must remain receptive to new knowledge.
In evolutionary terms, a language is like a species. If it doesn't adapt to changing conditions, it goes extinct. Different words or terms are like molecules or genes that form new combinations that prove useful or not. Try them out—if they don't work, try out another combination.
Downside? What you learned in literature or history a year ago may still be sort-of true but what you learned must be ready to change or be refitted, even if the book or event you're studying was long ago.
If you finish undergraduate studies, work a few years, then return for graduate studies in literature, you may find the terms have changed in a couple of ways:
Usually these changes aren't sudden, radical, or random, but only evolutionary—languages evolve like ecosystems. (analogy)
Purposes of terminology: Among students of any subject, terms can serve as shorthand for what has already been learned and need not be reviewed. When a student uses a term properly, listeners who are similarly trained can process a lot of information through a single word.
In contrast, discussing literature without terms requires extensive explanations at every step, "reinventing the wheel" at every turn.