Amaranth (Amaranthus cruentus)
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Amaranthus, collectively known as amaranth or pigweed, is a cosmopolitan genus of herbs. Approximately 60 species are presently recognised, with inflorescences and foliage ranging from purple and red to gold. Members of this genus share many characteristics and uses with members of the closely related genus Celosia.
Although several species are often considered weeds, people around the world value amaranths as leaf vegetables, cereals and ornamentals.
The word comes from the Greek amarantos (Αμάρανθος or Αμάραντος) the “one that does not wither”, or the never-fading (flower).
Amaranthus shows a wide variety of morphological diversity among and even within certain species. Although the family (Amaranthaceae) is distinctive, the genus has few distinguishing characters among the 70 species included.  This complicates taxonomy and Amaranthus has generally been considered among systematists as a “difficult” genus. 
Formerly, Sauer (1955) classified the genus into 2 sub-genera, differentiating only between monoecious and dioecous species: Acnida (L.) Aellen ex K.R. Robertson and Amaranthus.  Although this classification was widely accepted, further infrageneric classification was (and still is) needed to differentiate this widely diverse group.