obligatory

UK: /əˈblɪgətəri/

US: /əˈblɪgəˌtɔri, ˈɑblɪgə-/

US: (ə blig′ə tôr′ē, -tōr′ē, ob′li gə-)

WordReference Random House Learner's Dictionary of American English © 2026

o•blig•a•to•ry /əˈblɪgəˌtɔri, ˈɑblɪgə-/   adj. 

1. required;
   necessary;
   mandatory;
   compulsory:
   obligatory payment of taxes.

See -lig-.

WordReference Random House Unabridged Dictionary of American English © 2026

o•blig•a•to•ry  (ə blig′ə tôr′ē, -tōr′ē, ob′li gə-), adj. 

1. required as a matter of obligation; mandatory:
   A reply is desirable but not obligatory.
2. incumbent or compulsory (usually fol. by on or upon):
   duties obligatory on all.
3. imposing moral or legal obligation;
   binding:
   an obligatory promise.
4. creating or recording an obligation, as a document.

• Late Latin obligātōrius binding, equivalent. to Latin obligā(re) to bind (see obligate) + -tōrius -tory¹
• late Middle English 1425–75

ob•lig•a•to•ri•ly  (ə blig′ə tôr′ə lē, -tōr′-, ob′li gə-, ə blig′ə tôr′ə lē, -tōr′-, ob′li gə-), adv.  ob•lig′a•to′ri•ness, n. 
Synonyms

• 2. necessary, imperative.

Antonyms

• 2. voluntary.

Collins Concise English Dictionary © HarperCollins Publishers::

obligatory / ɒˈblɪɡətərɪ -trɪ/ adjective

1. required to be done, obtained, possessed, etc
2. of the nature of or constituting an obligation

obˈligatorily adverb