Rare species can be defined as any animal or plant that is scarce or uncommon in a particular region or habitat. These creatures are often considered endangered or threatened due to various factors such as habitat loss, predation, and global climate change. Some synonyms for the term rare species include endangered species, vulnerable species, and critically endangered species. These terms are often used interchangeably to describe different levels of conservation status for various species. Additionally, the term rare species can also be substituted with the word unusual, uncommon, or unique species, which can be used to describe species that are not necessarily endangered but are still considered rare or unusual.