- required as a matter of obligation; mandatory: A reply is desirable but not obligatory.
- incumbent or compulsory (usually followed by on or upon): duties obligatory on all.
- imposing moral or legal obligation; binding: an obligatory promise.
- creating or recording an obligation, as a document.
- required to be done, obtained, possessed, etc
- of the nature of or constituting an obligation
adj.c.1400, from Old French obligatoire “creating an obligation, obligatory,” and directly from Late Latin obligatorius “binding,” from obligat-, past participle stem of obligare (see oblige).