Origin: 1425–75; late Middle English <
Late Latin obligātōrius binding, equivalent to
Latin obligā(
re) to bind (
see obligate) +
-tōrius -tory1 Related formsob·lig·a·to·ri·ly /əˈblɪgəˌtɔrəli, ‐ˌtoʊr‐, ˈɒblɪgə‐, əˌblɪgəˈtɔrəli, ‐ˈtoʊr‐, ˌɒblɪgə‐/ Show Spelled[uh-blig-uh-tawr-uh-lee, ‐tohr‐, ob-li-guh‐, uh-blig-uh-tawr-uh-lee, ‐tohr‐, ob-li-guh‐] Show IPA, adverb ob·lig·a·to·ri·ness, noun
non·ob·lig·a·to·ri·ly, adverb
non·ob·lig·a·to·ry, adjective
un·o·blig·a·to·ry, adjective
Synonyms
2. necessary, imperative.
Antonyms
2. voluntary.