1 somebody 常用于口語, someone 常用于書面語,somebody 和someone 不可同of短語連用。
Somebody is standing over there. 有人在那邊站著。
There is someone waiting for you. 有人在等你。
2 some one 常同of短語連用,表示“某人”。
Some one of them didn't go to the party. 他們中有人沒有去參加晚會。
Some one of my friends will help you. 我有位朋友會幫助你。