The Collaborative International Dictionary of English v.0.48:

Adequateness \Ad"e*quate*ness\, n.
   The quality of being adequate; suitableness; sufficiency;
   adequacy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

adequateness
    n 1: the quality of being able to meet a need satisfactorily:
         "he questioned the adequacy of the usual sentimental
         interpretation of the Golden Rule" [syn: adequacy,
         adequateness] [ant: inadequacy, inadequateness]