卫生类：基础语法every和each
every是形容词，只能作定语修饰单数名词，意思是“每一个”，表示整体概念；
each是形容词、代词，可用作主语、宾语、定语等，意思是“每个”或者“各个”，表示单个概念；each可以放在名词前，可以后跟of短语，与动词同时出现时要放在“be动词、助动词、情态动词”之后或者行为动词之前
every和each都用作单数理解，但是下文中既可以用单数的代词(如he/him/his)也可以用复数的代词(如they/them/their)替代。如：Every one of the students in his class studies very hard.(他班上每个学生学习都很用功) / They are very busy. Each of them has something to do.(他们很忙，人人都有事干)