by oneself

1. 单独地

The little boy went out by himself.

小男孩独自一人出去了。

for oneself

1. 为自己

She kept the largest apple for herself.

她把最大的苹果留给自己。

to oneself

1. 独用

When I dine in a restaurant, I like a table to myself.

我上饭馆吃饭时喜欢一个人占一张桌。