-or

a suffix occurring in loanwords from latin, directly or through anglo-french, usually denoting a condition or property of things or persons, sometimes corresponding to qualitative adjectives ending in -id4, (ardor; honor; horror; liquor; pallor; squalor; torpor; tremor); a few other words that originally ended in different suffixes have been -ssimilated to this group (behavior; demeanor; glamour).
usage note
-or2
a suffix forming animate or inanimate agent nouns, occurring originally in loanwords from anglo-french (debtor; lessor; tailor; traitor); it now functions in english as an orthographic variant of -er1 , usually joined to bases of latin origin, in imitation of borrowed latin words containing the suffix -tor, (and its alternant -sor). the -ssociation with latinate vocabulary may impart a learned look to the resultant formations, which often denote machines or other less tangible ent-ties which behave in an agentlike way: descriptor; plexor; projector; repressor; sensor; tractor .
origin
-or1
suffix
a person or thing that does what is expressed by the verb actor, conductor, generator, sailor
word origin
via old french -eur, -eor, from latin -or or -ātor
-or2
suffix
indicating state, condition, or activity terror, error
the us spelling of -our
-or
suffix forming nouns of quality, state, or condition, from m.e. -our, from o.fr. -our (fr. -eur), from l. -orem (nom. -or), a suffix added to pp. verbal stems. also in some cases from l. -atorem (nom. -ator). in u.s., via noah webster, -or is nearly universal (but not in glamour, curious, generous), while in britain -our is used in most cases (but with many exceptions: author, error, senator, ancestor, horror etc.). the -our form predominated after c.1300, but mencken reports that the first three folios of shakespeare’s plays used both spellings indiscriminately and with equal frequency; only in the fourth folio of 1685 does -our become consistent. a partial revival of -or on the l. model took place from 16c. (governour began to lose its -u- 16c. and it was gone by 19c.), and also among phonetic spellers in both england and america (john wesley wrote that -or was “a fashionable impropriety” in england in 1791). in the u.s., noah webster criticized the habit of deleting -u- in -our words in his first speller (“a grammatical inst-tute of the english language,” commonly called the blue-black speller) in 1783. his own deletion of the -u- began with the revision of 1804, and was enshrined in the influential “comprehensive dictionary of the english language” (1806), which also established in the u.s. -ic for british -ick and -er for -re, along with many other attempts at reformed spelling which never caught on (e.g. masheen for machine). his attempt to justify them on the grounds of etymology and the custom of great writers does not hold up. fowler notes the british drop the -u- when forming adjs. ending in -orous (humorous) and derivatives in -ation and -ize, in which cases the latin origin is respected (e.g. vaporize). when the americans began to consistently spell it one way, the british hardened their insistence on the other. “the american abolition of -our in such words as honour and favour has probably r-t-rded rather than quickened english progress in the same direction.” [fowler]