by itself
phraseUK /baɪ ɪtˈsɛlf/
US /baɪ ɪtˈsɛlf/
Alone, with no one or nothing else around.
The little cat sat by itself on the warm porch.
OTHER MEANINGS
2. Without any help from anyone or anything.
The robot can clean the whole room by itself.
3. Used to say something is separate or not part of a group.
That one red apple is sitting by itself in the bowl.
4. Used to say something happens automatically, without a person doing it.
The door opens by itself when you walk near it.