What is the term that describes what happens before a climax in a novel?
There are two possibilities for the term you're looking for. One is "exposition," which is the basic narrative or story line. The other, which I think is what you want, is called "rising action." All of the story up to the moment of the climax is referred to as rising action. Visualize a short story or a novel as a triangle. The rising action begins at the lefthand base, and it rises up to the climax. The falling action and resolution descend down from the right side of the climax.
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"Rising Action" is the term used to describe the sequence of events that precede the climax. It is important not to confuse this with the story's middle, and can be distinguished usually because it occurs right before the climax, or "turning point" of the novel, which is considered the most pivotal point in sequence of events that take place throughout the story.