weak: applies to deficiency or inferiority of strength or power of any sort: a ~ government likely to topple soon.
feeble: suggests extreme weakness inviting pity or disdain: a ~ attempt to resist the enemy attack.
frail: implies delicacy and slightness of constitution or structure and liability to failure or destruction: a once robust man now ~ with disease.
fragile: suggests frailty, inability to resist rough use, and liability to destruction: a ~ beauty that the camera can't convey.
infirm: suggests instability, unsoundness and insecurity due to loss of strength from old age, crippling disease or temperamental vacillation: a ~ old woman confined to her home.
decrepit: implies being worn-out or broken down from long use or old age: the ~ butler had been with the family for years.
weak虚弱: 任何缺少力量，feeble: 极度虚弱，让人可怜或鄙视，frail脆弱: 质地单薄容易毁坏，fragile: 脆弱、不耐用、易毁坏，infirm: 由于年老疾病性格摇摆而不稳定不健康不安全，decrepit: 长期使用或年老，导致磨损崩塌
记忆方法: 1） 首字母WFFFID，排列成DIFF(不同) FW(服务)，需要不同的服务<==虚弱的人
2） 第一组虚弱的意思是无法承受紧张压力行动mean not strong enough to endure strain, pressure or strenuous effort. (strenuous 1、奋力 2、费力)
#------------------------第---二---组---------------------------
weaken: may imply the loss of physical strength, health, soundness, or stability OR of quality, intensity or effective power: a disease that ~ the body's defenses against infection.
enfeeble: implies an obvious and pitiable weakening to the point of helplessness: so ~d by arthritis that he requires constant care.
debilitate: suggests a less marked or more temporary impairment of strength or vitality: the operation has a temporary ~ing effect.
undermine: suggests a weakening by something working surreptitiously or insidiously, and implies a caving in OR breaking down: a poor diet ~s your health. (surreptitious鬼鬼祟祟,悄悄,常违反法律习俗，如he made a surreptitious entrance to the club他鬼鬼祟祟的进了俱乐部) (insidious: 潜藏但有害an insidious enemy阴险敌人)
sap: is close to undermine but adds a suggestion of draining of strength: drugs had ~ped his ability to think.
cripple: implies the causing of a serious loss of functioning power through damaging or removing an essential part or element: inflation had ~d the economy.
disable: suggests a usually sudden crippling or enfeebling of strength or competence: the ~d soldiers received an immediate discharge.
weaken: 丧失人体力量健康稳定或属性强度效力，enfeeble: 虚弱到可怜无助的地步，debilitate: 暂时的相对的弱化，undermine: 偷偷的或阴险的削弱，暗示塌陷(cave in)或倒塌(break down)，sap: 同undermine，但暗示耗尽力气，cripple: 损坏基础部分，导致功能丧失，disable: 通常表示突然的严重的损坏
记忆方法: 1）首字母WEDUSCD更改排序Wo USED DianChi: 我用过的电池<==电流弱化
2）第二组弱化的意思是使丧失力量能量活力mean to lose strength, energy, or vigor.
