what is a replicant in blade runner

In the Blade Runner franchise, replicants are bioengineered humanoids that are physically indistinguishable from adult humans. They are created to serve as slave labor in a variety of roles. Replicants are genetically engineered and created artificially, but they are not robots inside, as they are biological creatures who are manufactured. They are considered "machines," but they are not quite robots in the sense we usually think of the term. Prior to the events of the first Blade Runner film, replicants became illegal on Earth after a bloody off-world mutiny. The film focuses on the pursuit of six escaped replicants by Rick Deckard, a type of fictional police officer/bounty-hunter called a "Blade Runner," who investigates, tests, and executes replicants. Replicants have a limitation on their lifespans of four years in order to keep them from rising up against their creators. A primary element of the Blade Runner film is the ambiguity over whether the protagonist, Deckard, is a human or a replicant, which ties into one of the central themes of the film: the nature of humanity.