1. 弱的，无力气的，易毁坏的，容易被击败的　 lacking strength or power; easily broken, bent or defeated
2. 功能不佳的　 not functioning properly
3. 无说服力的，无力的　 not convincing or forceful
4. 稀的，稀释的　 containing a high proportion of water; dilute
5. 未达高标准的，有缺陷的　 not achieving a high standard; deficient

　～ answer　缺乏说服力的回答
　～ character　优柔寡断的性格
　～ coffee　淡咖啡
　～ constitution　虚弱的体质
　～ defence　不牢固的防御工事
　～ fort　不坚固的堡垒
　～ heart　心脏衰弱
　～ pretext　经不起推敲的托词/cn>
　～ railing　不牢固的栏杆
　～ soup　稀汤
　～ spots　弱点
　～ voice　微弱的声音

副词+～

　a little ～　差一点
　rather ～　有点虚弱
　so ～　如此虚弱
　still ～　依然虚弱

～+动词不定式

　～ to hold up roof　无法支撑房顶
　～ to say a word　虚弱得不能说话
　～ to walk　无力走路

～+介词

　～ at　在…方面弱的
　～ from　由于…而虚弱的
　～ in　在…方面弱〔差〕的
　～ in geography　地理知识薄弱
　～ in hearing　听觉差
　～ in mathematics　数学差
　～ in spelling　拼写差
　～ in the legs　腿无力
　～ of understanding　理解力差
　～ on name　记不住名字
　～ with　由于…而虚弱的
　～ with hunger　饿得身体虚弱

　She spoke in a weak voice.　她有气无力地说话。
　Don't stand on that chair, it's got a weak leg.　那张椅子有一条腿不结实，不要站在上面。
　We need strong leaders, not weak ones.　我们需要强有力的而不是软弱的领导。
　A weak fort can be easily captured.　不坚固的堡垒很容易被攻破。
　That was an incredibly weak answer.　那是一个令人难以置信的缺乏说服力的回答。
　"Stepped" is a weak form. 　stepped是规则变化的形式。
　Her pulse is weak; she must be very ill.　她的脉搏微弱，必定病得很厉害。
　She is not so weak as she looks.　她并不像看上去的那么虚弱。
　I'm very weak when it comes to giving up cigarettes.　在戒烟问题上我意志很弱。
　The young man is rather weak and may be easily led astray by bad companions.　这位年轻人意志薄弱，很容易被坏人引入邪路。
　The arguments in favor of the proposal are very weak.　赞成这个建议的观点没有说服力。
　Her French is rather weak.　她的法语相当差。
　The tea is weak.　这茶很淡。
　The play was well acted, but I thought the plot was a bit weak.　这部戏演得不错，但我认为戏的情节平淡了一点。
　She was weak from a long illness.　她因长期生病而十分虚弱。
　She is weak in the legs.　她感到两腿软弱无力。
　The supports were too weak for the weight of the load.　所载的分量很重，已经不住了。
　The old man is weak in body but not in mind.　这位老人体衰而心不老。
　She is weak in classic literature.　她不懂古典文学。
　Her school report shows that she is weak at arithmetic and biology.　从她的学习成绩单可以看出她算术和生物成绩差。
　She is a little weak in spelling.　她在拼写方面较差。
　I am weak on names.　我记不住名字。
　The flu victim was too weak to walk.　这位流感病人虚弱得连路都走不动。
　The walls are too weak to hold up the roof.　这些墙太不结实，支撑不了房顶。
　The teacher's so weak that the children do what they like.　这老师太软弱了，孩子们因此可以为所欲为。

 ♣ a weak moment
　易被说服或诱惑的时刻　time when one is unusually easily persuaded or tempted
　In a weak moment, I agreed to pay for her holiday.　我一时心软，同意了支付她度假的费用。
 ♣ weak at the knees
　一时两腿发软站不住　temporarily hardly able to stand because of emotion, fear, illness, etc.
　"How do you feel?" "Fine, really; a bit weak at the knees, but that will soon pass."　“你觉得怎么样?”“很好，真的，就是有点站不稳，不过很快会过去的。”
　Rudolph Balentino, the Adonis of the silent films, had one great quality— to make women feel weak at the knees.　鲁道夫·瓦伦丁诺，这部无声电影中的美男子，有一个绝妙的本事——使女人感到膝头发软。
 ♣ weak in the head
　愚蠢的　stupid
　You must be weak in the head if you think I'll agree to that.　如果你以为我会同意那事，你一定是脑子不管用了。
　Since John met that girl he's gone weak in the head.　约翰自从遇见那姑娘之后，变得有些糊里糊涂了。

 ♣ weak, feeble, infirm
　这三个词的共同意思是“弱的”。其区别是：weak用于修饰人、人的身体及其各部分器官，为最普通用语；feeble多指体格、脉搏、声音等“虚弱的，无力气的”，语气较weak强且庄重。例如：
　Her pulse was very feeble.　她的脉搏很微弱。
　infirm　特指因年老而衰弱。例如：
　My grandpa is infirm with age.　我祖父年老体衰。

　他的视力和听力都很差。
　［误］ He is weak at sight and hearing.
　［正］ He is weak in sight and hearing.
　［析］ 表示“在…方面差”，应该说be weak in，其中in不能改成at.

　［派生词］ weakly adv.软弱地；无力地；疲软地
　［同义词］ delicate, feeble, fragile, frail, infirm, weakened
　［反义词］ powerful, strong
　［词源］　古英语wac（弱）