Source : Webster's Revised Unabridged Dictionary (1913)

Calendula \Ca*len"du*la\, n. [NL., fr. L. calendae calends.]
   (Bot.)
   A genus of composite herbaceous plants. One species,
   {Calendula officinalis}, is the common marigold, and was
   supposed to blossom on the calends of every month, whence the
   name.

Source : WordNet®

calendula
     n : any of numerous chiefly annual herbs of the genus Calendula
         widely cultivated for their yellow or orange flowers;
         often used for medicinal and culinary purposes