动词过去式:challenged 过去分词:challenged 现在分词:challenging 第三人称单数:challenges 形容词:challengeable
1 ~ (to sb) (to do sth) invitation or call (to sb) to take part in a game, contest, fight etc to prove who is better, stronger, more able, etc 约请或要（某人）参加比赛、竞赛、战斗等以证明谁更好、更强、更能干等; 邀请比赛; 挑战
*issue/accept a challenge 发出[接受]挑战.
2 order given by a sentry to stop and say who one is 哨兵发出的止步命令, 并问来者是谁
*The sentry gave the challenge, `Who goes there?' 哨兵查问
3 ~ (to sth) statement or action which questions or disputes (sth) 对（某事物）表示怀疑或争论的言论或行为异议; 质问; 怀疑
*a serious challenge to the Prime Minister's authority 对首相的权威性郑重提出的异议.
4 difficult, demanding or stimulating task 艰巨的、高难度的或有激励性的任务
*She likes her job to be a challenge. 她喜欢艰巨的工作.
* Reducing the gap between rich and poor is one of the main challenges facing the government. 缩小贫富之间的差距是政府面临的主要难题之一.
5 formal objection, eg to a member of a jury 正式的反对（如反对陪审团的一个成员）.
1 [Tn, Tn.pr, Dn.t] ~ sb (to sth) invite sb to do sth (esp to take part in a contest or to prove or justify sth) 要求某人做某事（尤指参加竞赛或证明某事正当）
*challenge sb to a duel, a game of tennis 要求某人参加决斗、网球赛
* She challenged the newspaper to prove its story. 她要求这家报纸证实报道的真实性.
2 [Tn] order (sb) to stop and say who he is 命令（某人）停步并说出是谁; 问口令
*The sentry challenged the stranger at the gates. 哨兵查问在门口的陌生人.
3 [Tn] question the truth, rightness or validity of (sth); dispute 怀疑（某事）的真实性、正确性或有效性; 提出异议
*challenge sb's authority/right to do sth 怀疑某人是否有权力[权利]做某事
* challenge a claim, an assertion, a verdict 对某要求、主张、判决质疑
* This new discovery challenges traditional beliefs. 这项新的发现对传统观念提出了异议.
4 [Tn] test the ability of (sb); stimulate 考验（某人）的能力; 激励; 鞭策
*The job doesn't really challenge him. 这项工作不能真正考验 他.
5 [Tn] make a formal objection to (esp a member of a jury) 宣布反对（尤指陪审团某成员）.
1. What a challenge I must have been to this young teacher! 对这位年轻老师来说，教我这样一个学生一定是一件非常困难的工作啊!
2. The rise of acquired immune deficiency syndrome (AIDS) around the earth has represented a major challenge to medical progress both in developed and in less — developed countries. 全球艾滋病的蔓延无论在发达国家还是在欠发达国家都是对医学进步的重大挑战。
3. Then last year, she decided to challenge Embu's mayor, a veteran politician. 接着在去年，她决定挑战恩布市市长，一位资深政客。
4. Another kind of challenge faced the Egyptians between 4,000 and 5,000 years ago when they decided to build the first Pyramid. 四千到五千年之前，埃及人建造第一座金字塔时面临着另外一种挑战。
5. And many of us are interested in the challenge of space. 我们很多人还对来自太空的挑战深感兴趣。
6. A fixed stare can seem like aggressive behavior if it is a challenge as to who will look away first. 目不转睛的盯视会被看成是一种攻击性的行为，仿佛双方是在比拼，看谁先把目光移开。
7. "The problem is that to improve balance, you've got to challenge balance, which is always risky," says Mary E. Tinetti of the Yale University School of Medicine, "问题是，要提高平衡能力，就得首先挑战平衡。这样做总是有风险。"耶鲁大学医学院的玛丽·E. 蒂内提说。
8. "I challenge that. You didn't do either your grammar or your spelling homework." "我有意见，你没做语法作业，也没有做拼写练习。"
9. "The challenge is telling things people already know — and at the same time making it different," the spokesman said. 这位发言人说："难的是要将人们已熟知的事说得让它听起来不同。"
10. Medical science faces the challenge of conquering the many diseases which still attack human beings. 医学界面临着征服那些侵害人体的多种疾病的挑战。