[noun]If you have not signed a contract, you are under no obligation to (= it is not necessary to) pay them any money. [U + to infinitive]You have a legal obligation to (= The law says you must) ensure your child receives a proper education. [C + to infinitive]I haven't got time to do his work for him - I've got too many obligations (= things I must do) as it is. [C]
OBLIGATION
Meaning of OBLIGATION in English
Cambridge English vocab. Кембриджский английский словарь. 2012