(1) each用作形容词或代词，是“单个”的意思
用于两个或两上以上的人或物，侧重于个体或个性，在句中作主语、同位语、定语或宾语。Every只 用作形容词，是“每一个”的意思，用于三个以上的人或物，侧重于全体、 整体或共性。在句中只能作定语，放在名词前。
Eg: On each ( = every ) side of the square there are flowers. 在广场四周都是鲜花。
On each side of the road there are many trees. 路的两边有许多树。(不能用every)
Every student is here. = All the students are here. 所有的学生都到了。(强调整体) Each of the students has two pens. 每个学生都有两支钢笔。(强调个体)
(2) both, all, either, neither 的用法区别
both指“两者都”，表肯定;all指“三者或三者以上都”，表肯定;either指(两者中的)“任意一个”;neither指(两者)“都不”，表全部否定。
both后接复数名词，谓语动词用复数。All 后接可数名词复数或不可数名词，谓语动词视名词而定。Either 和 neither 后面的名词只用单数，作主语时，谓语动词也只用单数。例如; All ( of ) the students are good at English. 所有的学生都擅长英语。
Both ( of ) his parents are teachers. = His parents are both teachers. 他的父母都是老师。
Either of the answers is right.
= Either answer is right. = Both answers are right. 这两个答案都对。
Neither of the answers is right. = Neither answer is right. 两个答案都不对。