1. (n.) Want of validity or cogency; want of legal force or efficacy; invalidness; as, the invalidity of an agreement or of a will.

2. (n.) Want of health; infirmity.

advanced age advanced years adynamia age of retirement an incurable disease anemia anility atony blah feeling bloodlessness brain fag cachexia cachexy caducity chronic ill health cowardice debilitation decline of life declining years decrepitude delicacy delicate health disease dotage dullness eld elderliness enervation enfeeblement etiolation exhaustion eyestrain faintness fatigue feebleness flabbiness flaccidity fragility frailty goneness green old age hale old age healthlessness heart strain hoary age hypochondria hypochondriasis ill health impotence infirm old age infirmity infirmity of age invalidism invalidity jadedness languishing languishment languor lassitude listlessness longevity malaise mental fatigue mental strain morbidity morbidness old age oldness overstrain overtiredness peakedness pensionable age poor health prostration ricketiness ripe old age second childhood senectitude senility senior citizenship sickliness sleepiness sluggishness softness stance fatigue strain strengthlessness superannuation the downward slope the golden years tiredness unhealthiness unsoundness unwholesomeness vale of years valetudinarianism wasting weakliness weakness wearifulness weariness white hairs