A humanoid is a non-human entity with human form or characteristics. The term "humanoid" comes from the English words "human" and "-oid," meaning "resembling". Although there are no known humanoid species outside the genus Homo, the theory of convergent evolution speculates that different species may evolve similar traits, and in the case of a humanoid, these traits may include intelligence and bipedalism and other humanoid skeletal changes, as a result of similar evolutionary pressures. In science fiction, the term "humanoid" is used to refer to a being having human form or characteristics. In Dungeons & Dragons, "humanoid" is a creature type that includes certain human-shaped creatures, but excludes others for various reasons.