Errr, it might help to actually read the dictionary, and more than just the first definition:
verb
- simple past tense and past participle of bind.
adjective
- tied; in bonds:
a bound prisoner.
- made fast as if by a band or bond:
She is bound to her family.
- secured within a cover, as a book.
- under a legal or moral obligation:
He is bound by the terms of the contract.
- destined; sure; certain:
It is bound to happen.
- determined or resolved:
He is bound to go.
I assume you can see how most of these aside from 5 apply. The verb definition also fits directly what you are asking for…

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