While it is common wisdom that the goal of art is to stir emotions, the vocabulary of creative writing doesn’t always reflect that. MFA classes and craft essays teach us dozens of terms for character (foil, stock, antagonist, antihero, etc.) and plot (climax, denouement, twist, subplot, etc.), but leave us only a few ill-defined words for the actual emotional and psychological effects of a work on a reader.

Or at least that feels like the case in literary fiction. The horror genre provides a counterpoint, giving us an array of terms with which to dissect and understand one of the most primal human responses: fear.

Terror (left) and Horror (right) as drawn by Charles Darwin in The Expression of the Emotions in Man and Animals

One of the oldest distinctions in horror fiction is the difference between “terror” and “horror.” In their literary usage, these terms were famously defined by the Gothic writer Ann Radcliffe in her essay “On the Supernatural in Poetry.” Radcliffe, although mostly forgotten today, was a best-selling novelist who helped define and legitimize Gothic fiction—the genre from which horror descends. On the surface, horror and terror seem like synonyms, but Radcliffe argues that “Terror and horror are so far opposite, that the first expands the soul, and awakens the faculties to a high degree of life; the other contracts, freezes, and nearly annihilates them.”

So what is the difference? Terror is the feeling of dread and apprehension at the possibility of something frightening, while horror is the shock and repulsion of seeing the frightening thing. Terror is the sounds of unknown creatures scratching at the door; horror is seeing your roommate eaten alive by giant rats. Terror is the feeling a stranger may be hiding behind the door; horror is the squirt of blood as the stranger’s knife sinks in.

Many of the most iconic moments in horror fiction—Poe’s unseen beating heart, the unexplained noises in Hill House, Dracula slinking in the shadows—are driven by terror. They are partially obscured, letting our minds swell with tension and dread.

Why does terror enliven us while horror deadens? For Radcliffe, terror in its ambiguity moves us toward yet another effect: “the sublime.” The sublime is the confused awe at greatness and darkness our mind can’t grasp. We are both attracted and repelled by it. To Edmund Burke—whose philosophy Radcliffe references—it is “the strongest emotion which the mind is capable of feeling.” The sublime is often associated with nature—think hurricanes, looming mountains, the infinite expanse of the sea—yet it is particularly effective in art. This is because the mind requires a little distance to feel the sublime. If you are caught in a tornado, you may feel nothing except panic. But if you read a powerful description of a tornado destroying a town, you may feel the sublime.

Gothic scholar Devendra P. Varma elaborates the difference between terror and horror this way: “Terror thus creates an intangible atmosphere of spiritual psychic dread, a certain superstitious shudder at the other world. Horror appeals to sheer dread and repulsion, by brooding upon the gloomy and the sinister, and lacerates the nerves by establishing actual cutaneous contact with the supernatural.”

Works that bypass terror and rely on non-stop gore and shocks are often dismissed as “cheap thrills.” And it is true that horror is easier to achieve than terror. The loudest scream a horror film gets is the moment when, out of the blue, the killer leaps into the frame with a startling howl. It shocks you, but the shock is ephemeral. It does not stay with you, lingering in your mind like a proper moment of terror. (Think, for example, of the ambiguous, but foreboding, ending of Kubrick’s The Shining as we slowly pan into the ballroom photo.)

Stephen King, in Danse Macabre, adds a third effect: revulsion. He says, “I recognize terror as the finest emotion… and so I will try to terrorize the reader. But if I find I cannot terrify him/her, I will try to horrify; and if I find I cannot horrify, I’ll go for the gross-out. I’m not proud.”

Just as we understand terms like “protagonist” and “antagonist” in relation to each other, these emotional effects are best understood in how they play off of each other. King’s gross-out feeling, or revulsion, lets us think of these emotions as existing on a continuum. You are terrified when you come home and realize something is out of place. You are horrified when you find out your family has been murdered. You are revolted when you see the corpses teeming with maggots.

Terror often leads to horror, but the reverse is not necessarily the case. Indeed, horror—in showing us the frightening object so clearly—risks deflating all of the tension that terror builds up. If a writer wants to create terror, they have a delicate balancing act. Terror is built from ambiguity and from not-knowing, so the writer has to work to hide details from the reader, but without hiding so much that the effect is mere confusion. One must create the strange without lapsing into the silly or the impenetrable.

Here it’s useful to turn to yet another—yet closely related—concept: “the uncanny.” Famously delineated by Sigmund Freud, the uncanny is a hard-to-define emotion that arises from the familiar turning strange. In his essay, “The Uncanny,” Freud focuses on the bizarre and eerie fiction of ETA Hoffmann (a master of the eerie horror tale) and lists deja vu, unnatural repetitions, automatons, and doppelgangers as some techniques (in fiction) or occurrences (in reality) that bring about the feeling. We feel the uncanny as the barriers between things—life and death, dream and reality, body and mind—appear to crumble.

In German, Freud connects the term—unheimlich—to the concept of not belonging to the house. Haunted house stories often elicit the uncanny as the protagonists discover secret passageways and boarded-up rooms. The idea that one’s own home could have dark, hidden secrets produces uncanny unease. A great example of the uncanny in contemporary fiction is Brian Evenson’s “Windeye.” In that short story, a brother and sister find a mysterious window on the outside of their house that doesn’t lead to any room inside. When the sister touches it, she disappears, and no one else ever remembers her. Was she a figment of the brother’s imagination? Did reality split in two? The situation is infused with mystery, terror, and uncanny unease.

The uncanny, in its insistence of ambiguity and possible unreality, makes it similar to Radcliffe’s idea of terror. Of all the emotions one can experience, Freud argued that the uncanny might be the only one that is more powerful in fiction than in real life. And this powerful emotion is—like terror and horror or any other feeling—imparted by how the writer uses words on the page. A study of the psychology of these feelings, along with a study of how they are conjured by art, can only sharpen the tools a writer has to achieve that basic goal: making a reader feel.