/ ˌɒblɪˈgeɪʃn; NAmE ˌɑːb-/ noun
1.
[ U ] the state of being forced to do sth because it is your duty, or because of a law, etc. :
You are under no obligation to buy anything.
She did not feel under any obligation to tell him the truth.
I don't want people coming to see me out of a sense of obligation .
We will send you an estimate for the work without obligation (= you do not have to accept it) .
2.
[ C ] something which you must do because you have promised, because of a law, etc.
SYN commitment :
to fulfil your legal / professional / financial obligations
They reminded him of his contractual obligations.
We have a moral obligation to protect the environment.
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WORD ORIGIN
Middle English (in the sense formal promise ): via Old French from Latin obligatio(n-) , from the verb obligare , from ob- towards + ligare to bind.