Pressure means an external force to put on something. It is the Force applied per unit area.
pressure是压强的意思，是指外力施加到某物或某人。
stress is the internal(内部的) response to the external(外界的) action, it is caused due to the pressure that applies on it. Because it is the internal response, it can be used to describe mental(精神的) tension(紧张) and worry caused by problems in your life, work, etc. It is something that causes strong feelings of worry or anxiety(焦躁不安).
Stress是指因为被施加外力而自我感受到的压力。正好是pressure的接收者角色。强调的是接收者的感受，因此也用于表达生活中、工作中因为各种各样的困难导致的精神压力。
Strain is the effect of the stress. When it is too heavy, it will cause damage or bad effect.
Strain是指一个人因为自我感受到了stress压力而产生的精神紧张压力。
Force is something that tries to move things. It is a push or pull upon an object resulting in interaction(交互) with another object.
Force is strength or energy applied or brought to bear. It is a power or violence used on a person or thing. In this way, it can be describe military(军事的) strength. For example, Air Force.
Force是指两个物体之间的相互作用力，也引申为强制执行力，国家的力量，尤指军事力量。
Example:
The manager put pressure on the committee to finish the project in a week.
项目经理让团队一周内完成任务。
Team members were stressed.
整个团队成员感觉到了极大的项目压力。
The stress caused a great strain in the company. As a result, some employees quit from team, which caused a shortage of workers, and the stockholders(股东) have to fire the manager and hire a new one to let all calm.
这种压力导致了团队成员精神紧张不安。由此导致部分人离开了团队。大老板不得不开掉项目经理以平息大家的紧张压力。
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