The genus Amaranthus is in the Amaranthaceae Family of flowering plants. Plants of the World Online lists 99 accepted species in the genus Amaranthus.
Many Amaranths species share characteristics and uses with the Celosia genera, a member of the same family.
Various species in this family are grown for their ornamental flowers, some hanging downward and some resemble large “Celosia-like” flowers. The leaves and seeds are also used as a vegetable in some species. The grain is very nutritious and does not contain gluten. The leaves are an excellent source of vitamin A, C, calcium, manganese, and folate.
I am not going into all the history, at least not unless I get bored later. You can easily read more about the Amaranthus by typing it into your browser. The Wikipedia has lots of information.
