proportional: may apply to several closely related things that change without altering their relations: medical fees are ~ to one's income.  


proportionate: applies to one thing that bears a reciprocal relationship to another: a punishment not at all ~ to the offence.  


commensurate: stresses an equality between things different from but in some way dependent on each other: the salary will be ~ with experience.


commensurable: more strongly implies a common scale by which two quite different things can be shown to be significantly equal or proportionate: equal pay for jobs that are ~ in worth.      能较量的、可以同单位度量的


proportional按比例的: 成固定的比例，proportionate按比例的、相称的: 强调相互(reciprocal)相应的比例，commensurate相等的相当的: 强调事物相互关联，彼此相等，commensurable能比较的: 强调能用公共度量衡来显示事物彼此相等或相称(成比例)


记忆方法： 1）首字母PPCC联想为两台个人电脑2PC<==按比例使用

          2）比例的意思是事物间存在适当的比值mean in due ratio to something else.    ratio比值the relationship that exists between the size, number, or amount of two things and that is often represented by two numbers，表示数量之间的关系，通常用两个数字表示，如length-to-width ratio高宽比，如the ratioofstudents to teachers is 12 to 1师生比      这里due表示合适的appropriate or proper，如in due course/season在合适的地方/季节