To split hairs is a known idiom that means to argue about petty things. I looked into the etymology of the idiom but could not get to grips with the literal meaning. The comments assume the reader knows the literal meaning.

So does split hairs mean:

  • Arrange hair to make visible lines on the head?
  • Cut individual hairs?
  • Split one hair into two pieces either horizontally or vertically!


split hairs

to argue about very small differences or unimportant details

It's splitting hairs to tell people that they cannot lie but it is all right if they exaggerate.

Split hairs:

Make small and overfine distinctions:

- one of those medieval disputes which split hairs endlessly

- Yes, I do see the distinction and am perhaps splitting hairs over the delivery of the message.

- One sentence in the manual required that lawyers participating in the recount should ‘have the courage to voice disagreement and must split hairs trying to find faults.’

- I'm perhaps splitting hairs, here, but there has got to be a difference between drawing influence from various sources and plagiarizing.

  • 1
    I'm sure you'll be interested in this old dictionary: A new English dictionary on historical principles (vol 5, pt 1) by James Augustus Henry Murray. On page 24, HAIR 8.j. "To cut (or divide) the hair, to split hairs: to make fine or cavilling distinctions", and in quotes under 8.o. "j. 1652 SANCROFT Mod. Policies in D'Oyly Life (1821) II. 241 Machiavel cut the hair when he advised, not absolutely to disavow conscience, but to manage it with such a prudent neglect, as is scarce discernible from a tenderness." Commented Oct 23, 2014 at 11:20
  • Man, it's a hairy scary monster! I'd love to use it but only if it were incorporated into, say, a website like etymology online. I'm guessing you used the digitized version to copy all these scary references!
    – learner
    Commented Oct 23, 2014 at 15:12
  • 2
    Which way do you cut a log when you "split" it?
    – Octopus
    Commented Oct 23, 2014 at 15:56
  • That's an interesting question, though, it's for people who know how! I looked up the verb split and found out that it could also describe cutting things along the grain (=in the same direction as the grain). learned something new, thanks.
    – learner
    Commented Oct 23, 2014 at 16:42
  • 3
    One extra piece of evidence for the "cut lengthwise" meaning is that we say "split hairs" rather than "split hair"; by using the plural rather than the mass form, we emphasize the individuality of each hair and the act of cutting multiple individual hairs. Commented Oct 23, 2014 at 17:03

5 Answers 5


The image which the expression invokes is that of splitting a single hair along its length. If actually carried out, that would be a very tedious task, if not downright impossible, and would serve no obvious purpose. The expression thus characterises someone's very fine logical distinctions as a pointless waste of time.

  • 1
    Worth adding that someone with long hair might have to get a 1/2" haircut because she has "split ends," which are exactly this. This corroborates this interpretation of "split."
    – djechlin
    Commented Oct 24, 2014 at 5:50

If you literally split hairs, you split them from end to end. As a hair is already fine, it is difficult to split one, and the two halves of a split hair are very fine indeed.

This is why the metaphorical splitting of hairs refers to spending time on making very fine, and possibly unnecessary, differences.


I believe the idiom is based on the idea that the strand of hair is so fine that it would be difficult to create a blade with an edge sharp and fine enough to divide it lengthwise, as others have noted.

18th century examples combine it with other idioms all of which relate to the idea of impossibly fine work:

...making Chains for Fleas, Nets for Flies, and Instruments to unravel Cobwebs, and split Hairs.

See page 78 here: https://play.google.com/store/books/details?id=qwsUAAAAQAAJ&rdid=book-qwsUAAAAQAAJ&rdot=1


My guess is that expression is derived from a hairline distinction; as we are dividing a very fine line.


The expression is not meant to be taken literally but, as others have said, the implication must be that of splitting hairs lengthwise.

  • Your guess? The use of hairline distinction is significantly more recent that splitting hairs.
    – Chenmunka
    Commented Oct 24, 2014 at 14:06

I see the saying as being more accurate in the form of 'filleting hair'. When someone takes an argument, isolates one hair sized piece of it, fillets a sliver from it, and argues against it instead of anything important to the overall body of the argument, they are splitting hairs.

  • 2
    Welcome to ELL Richard. I think it would be helpful to explain a bit more about how filleting is different from splitting. It might not be clear to someone still learning English.
    – ColleenV
    Commented May 5, 2015 at 19:01

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .