An "unary operation" is a mathematical term that describes an operation or function that uses only one input. Other synonyms for this term include "unary function," "function of one variable," and "unary operator." Unary operations can be used in a variety of mathematical contexts to perform operations on a single number or element, such as squaring or negating a value. Some additional synonyms for "unary operation" include "monadic operation," "unary transformation," and "single operand function." These terms are all used interchangeably to refer to the same mathematical concept, which plays a critical role in many different areas of mathematical study.