explanatory

from WordNet (r) 3.0 (2006)

explanatory
    adj 1: serving or intended to explain or make clear;
           "explanatory notes"; "an explanatory paragraph"

from The Collaborative International Dictionary of English v.0.48

Explanatory \Ex*plan"a*to*ry\, a. [L. explanatorius.]
   Serving to explain; containing explanation; as explanatory
   notes. --Swift. Explat

from Moby Thesaurus II by Grady Ward, 1.0

31 Moby Thesaurus words for "explanatory":
      allegorizing, annotative, clarifying, critical, demonstrative,
      demythologizing, descriptive, discursive, editorial, elucidative,
      enlightening, euhemeristic, exegetic, exegetical, exemplificative,
      explaining, explicative, explicatory, expositional, expositive,
      expository, glossarial, illuminating, illuminative, illustrative,
      interpretative, interpretive, rationalistic, rationalizing,
      revelatory, scholiastic