Type of inflorescence in which all pedicles (floral stalks) eradiate from a common point. E.g., geranium, gardenia. One can also say the umbel is a raceme whose axis did not elongate: the younger flowers are in the center and the older gradually distal. (Also see Raceme, Inflorescence).
Undulated
Leaf or petal with wavy margin. The term is not applied to serrated or toothed margins.
Unisexual
Monoecious or Dioecious plants in which the flower are male or female; flower that is not hermaphroditic, but is either male or female. (compare with Hermaphrodite).
Palmate: Term used to name compound leafs with several leaflets that open like a fan from a common point, with the format of a flat hand. E.g., buckeyes.