Compound mutation, also known as a double mutation, is a genetic mutation that involves two or more distinct, independent mutations occurring at the same time. It can lead to more severe phenotypes and clinical outcomes than single mutations. There are many synonyms for the term compound mutation, including dual mutation, complex mutation, multiple mutation, simultaneous mutation, and double hit. These terms are often used interchangeably in medical research and clinical practice to describe the same phenomenon. Understanding the implications of compound mutations is important for genetic counseling and precision medicine, as it can affect treatment decisions and patient outcomes.