While searching for the correct spelling of inerrant, I came across a definition that labeled it as something that is unerring.

Why would something that is unerring be "inerrant" instead of "unerrant?"

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    I don't think this question is about etymology and word origins. This is a legitimate question that a user could ask as English is not consistent in placing prefixes. "Unhappy" vs "inhappy", "uncorrect" vs "incorrect", "unimportant" vs "inimportant".
    – user24743
    Commented May 31, 2016 at 17:22
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    I agree with @Rathony. The answer to a question shouldn't make the question off-topic.
    – ColleenV
    Commented May 31, 2016 at 17:27
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    Some of your confusion may be because although they are spelled similarly, to err is different from being errant. They both have some Latin roots, but come from different words in Middle English.
    – ColleenV
    Commented May 31, 2016 at 17:42
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    I can't think of any context where inerring, inerrant or unerrant wouldn't be better replaced by unerring. The "reason" why in- and -ant have lost out to un- and -ing here is essentially just a matter of established idiomatic preference. But that preference is so strong you don't really even need to think about those ultra-rare / obsolete alternatives. Commented May 31, 2016 at 18:12
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    @FumbleFingers but inerrant means 'incapable of erring/infallible', not necessarily 'committing no mistakes/consistently correct'. Besides it always makes me think of knight-errant :)
    – ColleenV
    Commented May 31, 2016 at 20:46

1 Answer 1


From what I could find, the word "unerring" came into use in 1640s from un-"not" + verbal noun from err (from Old French errer - "go astray, lose one's way; make a mistake; transgress").

The word "inerrant" came into use in 1650s, in reference to "fixed" stars (as opposed to "wandering" planets), from Latin inerrantem - "not wandering, fixed (of stars)", from in- "not, opposite of" and present participle of Latin errare ("to wander, stray, roam, rove"). Its usage as "unerring, free from error" began from 1785.

So, although the two words may be of the same origin (from Latin), they came into the English usage separately, each one by its own way.

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    Well, ultimately they are of the same origin; but the point is that one of them was formed in English from a Latin root, the other formed in Latin and taken over via French into English. Notice that "erring" already has English material in it ('-ing'). But there's no way to know in advance which negative words were taken from Latin or French, and which were formed in English: that's a historical accident.
    – Colin Fine
    Commented May 31, 2016 at 19:02

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