Antipernicious Anemia Factor is a term used to describe a substance that is essential in treating a specific type of anemia caused by a lack of vitamin B12. There are a few synonyms for this term that can be used interchangeably depending on the context. These include 'vitamin B12 factor', 'extrinsic factor', 'cobalamin', 'cyancobalamin', and 'factor III'. All of these terms refer to the same substance that helps the body absorb vitamin B12 from food or dietary supplements. While the technical terminology may vary, the importance of this substance in treating pernicious anemia cannot be overstated.