You need only look at the career of George Romero, who imbued his zombie movies with blunt social commentary on consumerism, race and Cold War militarism. When Mr. Romero (“Night of the Living Dead”) and Tobe Hooper (“The Texas Chain Saw Massacre”) died last year, horror lost two of its most important artists. They left behind movies that serve as a persuasive counterargument to the idea that horror cannot be righteous, funny or beautiful. They inspired generations of filmmakers, creating tropes of fear that have been adopted and refined, building a foundation for modern horror sturdy enough to support an incredibly diverse array of work, ranging from the queasy thrills of “Don’t Breathe” to the austere shocker “It Follows” to the psychological blood bath “Mother!”

In his review for The New York Times, A. O. Scott described “Mother!” as a comedy, but considering its outlandish gore, its debt to “Rosemary’s Baby” and the director Darren Aronofsky’s history with skewed-world terror, I see it as closer to horror.

Horror movies are nearly as old as film itself (the first “Frankenstein” movie was produced by Thomas Edison in 1910), and to be fair, over the last century, the definition of the horror movie has shifted and is still evolving. How do you define horror? It depends on what era you are referring to. Before the late 1960s, when someone referred to horror, they usually meant the supernatural. Carlos Clarens’s pioneering 1967 book, “An Illustrated History of the Horror Film,” made only brief mention of “Psycho” and “Peeping Tom” because they focused on humans, which, Mr. Clarens argued, put them outside the realm of what he considered “pure horror.”

In its current, mature incarnation, horror is applied to so many different kinds of movies that it’s harder than ever to pin it down. But the traditions of the classic Universal monster movies and the new horror of the 1970s remain influential on screens today. Horror deserves to be considered as a broad genre, not a niche that exists outside rooms where the most prestigious awards are given out. Guillermo del Toro, the greatest monster movie director alive, seemed to be making a similar case in “The Shape of Water,” a film widely described as a romance, with the lovers being a mysterious scaly beast and a woman played with terrific sensitivity by Sally Hawkins.