To Verb Strength Weakened  Weaken Weakened Make Loss

weak·en
\\ˈwē-kən\\ verb 
(weak·ened ; weak·en·ing \\ˈwēk-niŋ, ˈwē-kə-\\)transitive verb
1. to make weak : lessen the strength of
2. to reduce in intensity or effectiveness
intransitive verb
: to become weak
• weak·en·er \\ˈwēk-nər, ˈwē-kə-\\ noun
Synonyms.
  , , , , , ,  mean to lose or cause to lose strength or vigor.  may imply loss of physical strength, health, soundness, or stability or of quality, intensity, or effective power
      a disease that weakens the body's defenses
  .  implies an obvious and pitiable condition of weakness and helplessness
      enfeebled by starvation
   suggests a less marked or more temporary impairment of strength or vitality
      the debilitating effects of surgery
   and  suggest a weakening by something working surreptitiously and insidiously
      a poor diet undermines your health
      drugs had sapped his ability to think
   implies causing a serious loss of functioning power through damaging or removing an essential part or element
      crippled by arthritis
   suggests a usually sudden crippling or enfeebling
      disabled soldiers received an immediate discharge

weak·en
\ˈwēkən\ verb
(weakened ; weakened ; weakening \-k(ə)niŋ\ ; weakens)
Etymology: weak (I) + -en
transitive verb
1. : to make weak : lessen the strength of : 
 < disease weakens the body >
 < fatigue weakened his grip >
 < wetting weakens paper >
 < floodwaters weakened the foundations of the bridge >
 < doubts weakened his resolve >
 < hypotheses which … weaken rather than affirm purely mechanistic interpretations of nature — J.W.Krutch >
2. : to reduce in intensity or effectiveness
 < milk weakened one half to two thirds with plain boiled water — Morris Fishbein >
intransitive verb
1. : to become weak
 < steadily weakening storm >
: lose strength or spirit or determination : become less firm or resolute
 < the Middle West was weakening in its allegiance to the Democratic party — American Guide Series: Ind. >
2. : to change from a complex to a simple sound (as from a diphthong to a long vowel) : change from a strong to a weak sound : change from an open to a close vowel
Synonyms: 
 , , , , , ,  can mean, in common, to lose or cause to lose strength, vigor, or energy. : , the most general of the group, signifies the loss of physical strength, soundness, or stability, or, in extension, of quality, intensity, or effective power
  < weakened by failing health — C.H.Lincoln >
  < the days and nights of dissipation had weakened and depressed him — Louis Bromfield >
  < has left rural churches weakened in numbers and financial resources — American Guide Series: New York >
  < the spirit of adventure is not stimulated but weakened by poverty — M.R.Cohen >
   implies a more obvious condition, usually suggesting a helplessness or feebleness or forcelessness
  < despite an enfeebled body, the mental faculties … can remain intact to the very end of life — Current Biography >
  < can excessive reading actually enfeeble one's thinking apparatus — A.N.Whitehead >
  < the years had not enfeebled his acting — E.H.Collis >
   suggests a less marked, usually more temporary, impairment of strength or vitality
  < ivy debilitates trees, disintegrates mortar in walls and dislodges roof tiles — F.D.Smith & Barbara Wilcox >
  < avoid embroilments which debilitate our strength — Current Biography >
  < the fears and the rages that debilitate — H.A.Overstreet >
   and  suggest a weakening by the effects of some surreptitious or insidious force, often carrying the idea of a draining of strength or a slow caving in or breaking down
  < the members of his family undermined by dissipation, crime and madness — Times Literary Supplement >
  < the emotions which would have undermined and demoralized him had he not sworn beforehand to abjure that — Marcia Davenport >
  < a gradual oxidation of the rubber thread which undermines the quality of the rubber — Albert Thompson & Sigfrid Bick >
  , meaning basically to maim or mutilate, suggests a serious impairment of force or effect similar to if not greater than that caused by a loss of a limb to a person
  < the brain-injury victims, i.e., those who have been crippled by such things as blows, encephalitis, or a sustained high fever in infancy — Time >
  < a heavy winter snowfall cripples transportation — Corey Ford >
   implies any force that makes unfit or which incapacitates, especially suddenly
  < disabled for field work by an accident which resulted in the loss of his right leg — C.W.Mitman >
  < disabled the car so it wouldn't run — W.W.Haines >
  < an indifferent memory disabled him from mastering the Indian languages — Francis Parkman >