The Collaborative International Dictionary of English v.0.48:

Phonology \Pho*nol"o*gy\, n. [Phono- + -logy.]
   The science or doctrine of the elementary sounds uttered by
   the human voice in speech, including the various
   distinctions, modifications, and combinations of tones;
   phonetics. Also, a treatise on sounds.
   [1913 Webster]

WordNet (r) 3.0 (2006):

phonology
    n 1: the study of the sound system of a given language and the
         analysis and classification of its phonemes [syn:
         phonology, phonemics]