Verb

(head)

(oblige)

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Verb

(oblig)

To constrain someone by force or by social, moral or legal means.

I am obliged to report to the police station every week.

{{quote-Fanny Hill, part=3 , Tho' he was some time awake before me, yet did he not offer to disturb a repose he had given me so much occasion for; but on my first stirring, which was not till past ten o'clock, I was oblig'd to endure one more trial of his manhood.}}

To do someone a service or favour (hence, originally, creating an obligation).

He obliged me by not parking his car in the drive.

*

To be indebted to someone.

I am obliged to you for your recent help.

To do a service or favour.

The singer obliged with another song.