相机而动 seize the opportunity
Explanation
指观察时机，看到适当机会立即行动。强调根据具体情况灵活应变。
It means to observe the timing and act immediately when a suitable opportunity arises. It emphasizes the ability to respond flexibly to different situations.
Origin Story
话说三国时期，诸葛亮率领蜀军北伐，与曹军在渭水之畔展开激烈的对峙。曹军占据地利，兵力雄厚，蜀军处于劣势。诸葛亮深知硬拼难以取胜，便决定采取策略，相机而动。他暗中派人观察曹军的动向，并仔细分析地形地势。经过一段时间的观察，诸葛亮发现曹军主帅司马懿性格谨慎，多疑善变，常常因为一些小事而犹豫不决。诸葛亮抓住这个弱点，故意示弱，营造蜀军士气低落，准备撤兵的假象。司马懿果然上当，放松警惕，下令追击蜀军。诸葛亮早就预料到司马懿的举动，在预设的埋伏地点设下陷阱，待曹军进入伏击圈后，蜀军突然发起猛攻，大败曹军。这场战役以蜀军大胜告终，充分体现了诸葛亮“相机而动”的智慧。
During the Three Kingdoms period, Zhuge Liang led the Shu army on a northern expedition and engaged in a fierce standoff with the Cao army on the banks of the Wei River. The Cao army had a geographical advantage and a superior force, putting the Shu army at a disadvantage. Zhuge Liang knew that a direct confrontation would be difficult to win, so he decided to adopt a strategy of waiting for the right moment to act. He secretly sent people to observe the movements of the Cao army and carefully analyze the terrain. After a period of observation, Zhuge Liang discovered that the Cao army's commander-in-chief, Sima Yi, was cautious and indecisive, often hesitating over trivial matters. Zhuge Liang exploited this weakness, pretending to be weak and creating a false impression that the Shu army was demoralized and preparing to withdraw. Sima Yi fell for the trick, lowered his guard, and ordered a pursuit. Zhuge Liang had anticipated Sima Yi's actions, setting a trap at a pre-arranged ambush site. When the Cao army entered the ambush zone, the Shu army launched a sudden attack and decisively defeated the Cao army. The battle ended with a resounding victory for the Shu army, fully demonstrating Zhuge Liang's wisdom in waiting for the right moment to act.
Usage
用于形容人灵活应变，抓住机会
Used to describe a person's ability to respond flexibly and seize opportunities.
Examples
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他见时机成熟，便相机而动，果真成功了。
ta jian shiji chengshu,bian xiangji er dong,guo zhen chenggong le.
He took action at the right moment and succeeded.
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我们要根据市场变化，相机而动，才能立于不败之地。
women yao genju shichang bianhua,xiangji er dong,caineng liyu bu bai zhi di
We must adapt to market changes and act accordingly to succeed.