The term relict is used to refer to surviving remnants of natural phenomena. Compare relic which is used to refer to human artifacts or remains.
In biology a relict is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas. The distribution of a relict is characterized as endemic. The tuatara is an example of a relict. It now lives only on a few small islands off New Zealand. The term "relict" can also refer to an ancient species that survives while related species go extinct. The horseshoe crab is an example of this type of relict. Horseshoe crabs are most closely related to the eurypterids, which disappeared in the Permian-Triassic extinction event.
In ecology, an ecosystem which originally ranged over a large expanse, but is now narrowly confined, may be termed a relict.
In geology, the term "relict" refers to structures or minerals from a parent rock that did not undergo metamorphosis when the surrounding rock did, or to rock that survived a destructive geologic process. For example, the wavy patterns often seen in marble are relicts of layering in the original limestone.
A relict was also an ancient term for a widow, but has come to be a generic or collective term for widows and widowers.