Learner's definition of ITSELF
1 : that same one: a — used as the object of a verb or preposition to refer to something that has already been mentioned
b — used for emphasis to refer to something that has already been mentioned
The cat washed itself.
History keeps repeating itself.
The problem should work itself out.
The chain folds back on itself.
The restaurant has built quite a reputation for itself.
I found the envelope, but the letter itself was missing.
That itself was enough of an excuse.
The city itself is fairly small.
2 — used after a noun to say that someone or something has a lot of a particular quality
1 : on its own : without being directly controlled by a person 2 : with nothing nearby : alone
: in its own nature : when considered as something separate from other things : without anything else added
— see also an end in itself at 1end