An assertion is a confident statement or declaration that something is true. It is often used in discussions, arguments, or writing to express a belief or opinion. Assertions can be based on facts, personal experiences, or interpretations, but they do not always require evidence to support them. In logic and philosophy, an assertion is a proposition that can be evaluated as either true or false. In programming, particularly in languages like Python or Java, an assertion is a statement that checks if a condition is true during the execution of a program. If the condition is false, the program will typically raise an error or exception. This helps developers identify bugs and ensure that their code behaves as expected.