obligatory

Etymology

It is inherited from Middle English obligatorie,^[2] borrowed from Anglo-Norman obligatorie and obligatoire,^[3][4] also borrowed from Old French obligatoire (“creating an obligation”),^[2][3] and directly borrowed from Latin obligātōrius (“binding”).^[3][2][5][6] The Latin adjective, which the OED records from the 2nd century AD and Etymonline and Klein place in Late Latin, is formed from obligātus, the past participle of obligō (“to bind, put under obligation”), with -ōrius.^[3][2][5] The Latin verb is from ob- (“to”) and ligō (“to bind”), from Proto-Indo-European *leig- (“to tie, bind”).^[2] The Anglo-Norman adjective is recorded from 1284–86, of a legally binding bond;^[4] in Old French lettre obligatoire is recorded in 1320.^[3]

Earliest recorded meaning

Creating or constituting an obligation, chiefly in letter obligatory, a written bond or contract: about 1400, in a Middle English chronicle, the Brut.^[3][7]

Semantic evolution

The word began in legal language, in phrases like letter obligatory and writing obligatory, which match post-classical Latin littera obligatoria and scriptum obligatorium and the Anglo-Norman phrases.^[3][4] From 1502 it meant imposing an obligation, morally binding, compulsory rather than merely permitted,^[3][7] the main sense today.^[8][9] Johnson (1755) defined it as "imposing an obligation; binding; coercive", used with to or on.^[10] In biology it has been used since 1887 for obligate, restricted to one way of life.^[3][7] From 1917, often humorously, it describes something so customary or fashionable that it is expected every time.^[3]

Timeline

• c. 1400 – creating an obligation, in letter obligatory.^[3][2]
• 1502 – morally or legally binding; compulsory.^[3][7]
• 1755 – Johnson: imposing an obligation; binding.^[10]
• 1887 – biology, obligate.^[3][7]
• 1917 – humorously, so customary as to be expected, in Wharton.^[3]

Meanings

Adjective

1. Required by a law, rule or custom; compulsory: Helmets are obligatory on the building site.^[9][8][3]
2. Imposing or creating a duty or obligation, often with on or upon; in law, as in letter obligatory, a written bond.^[8][3][9]
3. Often humorous: so customary or fashionable as to be expected on every occasion: the obligatory selfie in front of the tower.^[3]
4. (biology) Restricted to a particular way of life; obligate.^[3][7]

Word family

• obligatorily
• obligatoriness
• nonobligatory
• unobligatory

Related words

• obligate
• obligation
• obligational
• obligato
• oblige
• obligee
• obliging
• obligor

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
3. ^ a b c d e f g h i j k l m n o p q r Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
4. ^ a b c Anglo-Norman Dictionary (AND2), Aberystwyth University, anglo-norman.net (2nd ed., 2005–)
5. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
7. ^ a b c d e f Kay, Christian; Roberts, Jane; Samuels, Michael; Wotherspoon, Irené, eds. (2009), Historical Thesaurus of the Oxford English Dictionary, Oxford: Oxford University Press; online edition (2024)
8. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
9. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins
10. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.