Source : Webster's Revised Unabridged Dictionary (1913)

Desideratum \De*sid`e*ra"tum\, n.; pl. {Desiderata}. [L., fr.
   desideratus, p. p. See {Desiderate}.]
   Anything desired; that of which the lack is felt; a want
   generally felt and acknowledge.

Source : WordNet®

desideratum
     n : something desired as a necessity; "the desiderata for a
         vacation are time and money"
     [also: {desiderata} (pl)]