A single-valued function is a type of mathematical function that has exactly one output value for every input value. Synonyms for this term include a univalent function, a one-to-one function, a one-to-one correspondence, and an injective function. In contrast, a multivalued function can have more than one output value for a single input value. Other synonyms for a multivalued function include a many-to-one function, a surjective function, and a function with more than one root or branch point. Single-valued functions are commonly used in a variety of fields, including calculus, geometry, and statistics, where they provide a precise and accurate way to describe relationships between variables.