Correlative

In grammar, correlatives are words that are separated in a sentence but function together to perform a single function.

In English, examples are both—and, either—or, neither—nor, the—the ("the more the better"), so—that ("it ate so much food that it burst"), and if—then. In the Romance languages, the demonstrative pro-forms function as correlatives with the relative pro-forms, as autant—que in French; in English, demonstratives are not used in such constructions, which depend on the relative only: "I saw what you did", rather than *"I saw that, what you did".