He is the implementor of the library.

He is the implementer of the library.

Which is correct?

  • 2
    It seems that both are correct, but I would like to know if there is any other difference, e.g. one more typical in BE and the other in AE. Jun 15, 2015 at 9:15
  • I'm trying to decide whether the repeated questions about "-er" vs "-or" are the acts of a tormenter or a tormentor.
    – Hot Licks
    Nov 13, 2016 at 3:40
  • 3
    My research brought me here. Thankfully there was a helpful answer, despite the fact that this question was closed....
    – Lumberjack
    Aug 28, 2018 at 11:27
  • This is the top Google result for Implementer vs Implementor circa 8/28/18.
    – Lumberjack
    Aug 28, 2018 at 11:28
  • @Lumberjack Yeah, even though probably 99% of traffic to SE is coming from people using a search engine and just trying to get, well, an answer to their question, moderation rules here seem focused on pleasing the 1 percent that actually hangs around on SE all day and gets annoyed by repeated/off-topic questions. I say if it is not useful, search engines will recognize it and it will just fall in ranking and thus be buried in the archives and get no points etc. So it would resolve itself anyway. Jul 23, 2019 at 9:03

2 Answers 2


They are both corrrct terms, "implementer" is now the more common between the two Ngram. It appears there is no difference in usage between AmE and BrE where implementer is equally common Ngram.

Both -or and -er are common suffixes which are used to make nouns out of adjectives:


  • word-forming element making nouns of quality, state, or condition, from Middle English -our, from Old French -our (Modern French -eur), from Latin -orem (nominative -or), a suffix added to past participle verbal stems.

  • 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.


  • English agent noun ending, corresponding to Latin -or. In native words it represents Old English -ere (Old Northumbrian also -are) "man who has to do with," from Proto-Germanic *-ari.

  • Generally used with native Germanic words. In words of Latin origin, verbs derived from past participle stems of Latin ones (including most verbs in -ate) usually take the Latin ending -or, as do Latin verbs that passed through French (such as governor); but there are many exceptions (eraser, laborer, promoter, deserter; sailor, bachelor), some of which were conformed from Latin to English in late Middle English.



they are alternative spellings of one another, so they are equivalent. Having said that, I would prefer

He implemented the library.

Unless you are trying to say something different, like he created and currently maintains the library, in which case something like:

He is the creator and maintainer of the library.

might be better.


Not the answer you're looking for? Browse other questions tagged or ask your own question.