So, on what finger do you wear a promise ring? In the USA and the UK, the ring finger (fourth finger) of the left hand holds the greatest significance; engagement rings and wedding rings are worn on this finger almost without exception.
In biology and ecology, extinction is the end of an organism or of a group of organisms (taxon), normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively.
When a species/animal is endangered it means that they are disappearing fast or have a very small population - not large enough to survive. Extinction means the end of existence for a species. The IUCN (International Union for the Conservation of Nature and Natural Resources) have compiled a Red List. This red list is a guide to how endangered a species is - animals are measured on a scale from 'Least Concern' to the worst, 'Extinct'; Least Concern - Near Threatened - Vulnerable - Endangered - Critically Endangered - Extinct in the Wild - Extinct.