noun
Etymology: so called from the fact that each blooms for only one day
1.
a. : a plant of the genus Hemerocallis being native to Europe and Asia but cosmopolitan in cultivation and as escapes, having complex tuberous roots and long narrow basal leaves, and bearing short-lived flowers that resemble lilies and are yellow or tawny orange in the wild but under cultivation have developed pinkish and mahogany to purplish forms
b. : the flower of a day lily
2. : plantain lily