Ⅰ. human being “人类”，可数名词，算数为human beings. 意义较具体，以区别于动物、鬼神之类。如：
There were no sight of human beings on the island although there were monkeys, wild goats and snakes. 那个岛上虽然有猴子，野羊和蛇，但没有人居住过的痕迹。
Ⅱ. man “人类”，单数或复数均可。其前不用限定词。如：
Man must make the earth support more people. 人类必须使地球养活更多的人。
Ⅲ. person. “人”着重指个别而言。与animal相对。指男，女，老，少均可。如：
There are only three persons in the room. 房间里只有三个人。
Ⅳ. people “人”是集合名词。与enemy相对，有较强的感情色彩。指普通人时，可与person代换。其复数形式为“民族”之意。如：
① Most people think so 大多数人这样想。
② There are more than 50 peoples in our country. 我国有50多个民族。