What term describes the validity of an algorithm based on a given specification?

The term that describes the validity of an algorithm based on a given specification is correctness. This concept refers to whether the algorithm consistently produces the expected results for all possible valid inputs as outlined in its specifications. Correctness ensures that the algorithm fulfills its intended purpose and adheres to the defined requirements, confirming that it operates as expected under specified conditions.

Functionality relates to the features and services provided by the software, not specifically its alignment with a specification. Stability usually refers to how well an algorithm performs under various conditions without failing, while robustness indicates an algorithm's ability to handle invalid inputs or unexpected situations gracefully. Thus, correctness is the most accurate term for the alignment of an algorithm's behavior with its specifications.