(n.) The quality or state of being dumb; muteness; silence; inability to speak.

anaudia aphasia aphonia asininity blockishness boobishness boorishness bovinity brevity briefness brusqueness cloddishness conciseness crassness crudeness curtness deaf-muteness denseness density dim-wittedness dimness doltishness dull-wittedness dullardism dullness duncery economy of words grossness hebetude inarticulateness laconicalness laconism lethargy loutishness lumpishness muteness mutism ninnyism oafdom oafishness obmutescence obtuseness opacity pauciloquy quietness quietude shortness silence simpletonianism slowness sluggishness sottishness sparingness of words speechlessness stolidity stupidity taciturnity terseness thick-headedness thick-wittedness tonguelessness unloquaciousness untalkativeness unteachability voicelessness wordlessness wrongheadedness yokelism