Smith and Ricardo typically referred to the value-determining ingredient simply as the “labour time” or the “quantity of labour” required for production. They did not explicitly use the term “socially necessary labour time” but rather focused on the idea that a commodity’s value was measured by the labour spent in its production under ordinary conditions. This notion was later refined by Marx into the concept of “socially necessary labour time,” which emphasizes that it is not any individual labour effort but the average amount of labour time required—reflecting prevailing social and technological norms—that determines value.