I was doing edit reviews on Stack Overflow and found out that people keeps correcting the word "boolean", replacing it with "Boolean" when it appears in text (but not in source code, of course). And then I found out that the spelling checker in my browser agrees with them.

Is there any rationale behind this? It seems grammatically incorrect.

I think the word boolean is used in two different ways, either among programmers as a simple noun, "return a boolean", or as part of a mathematical term, "boolean logic", "boolean algebra". None of these cases seem to motivate a capital letter. You don't write "return a Float", "Fuzzy logic" or "Linear algebra" (unless of course it is at the beginning of a sentence).

I suppose that the capital letter in "Boolean" somehow refers to the name George Boole. But then that doesn't make sense either. I found this link which gives some excellent examples of similar cases, where some term is named after a person, but no capital letter is used.

Any consensus? What is correct? What should we use?

  • Wikipedia says "Boolean", capitalized – gnat Apr 17 '13 at 9:28
  • Floats, fuzzy logic and and linear algebra aren't named after anyone. Boolean logic, Euclidean geometry and Euler's constant are. If you'd invented something, it might be called Lundinian, not lundinian. – Blrfl Apr 17 '13 at 10:31
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    From the English Language Usage stack exchange -- Should the word Boolean be capitalized? – user40980 Apr 17 '13 at 15:01
  • @Blrfl See the link posted. "shrapnel", "diesel", "saxophone", "baud", "ampere", "chauvinist", "nicotine" and so on. – user29079 Apr 17 '13 at 15:15
  • @MichaelT A site where the top answer is stating Wikipedia as an authority of the English language? No thank you :) – user29079 Apr 17 '13 at 15:17

I am not aware of any reference that advice boolean. You are correct, that it historically dates back to George Boole, but as far as I can tell, all spelling references agree on the adjective as well as the noun being written as Boolean.

Here are a few references:

Feel free to ask on english.stackexchange.com about the linguistic reasoning behind this, but there seems to be no official authority that accepts the lower-case version. They are all consent on the upper-case variant, so there is currently no reason for me to doubt the correctness of Boolean.

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    I suppose Oxford is the canonical reference. If they write Boolean there, then that's how it should be spelled, reason be damned. But to me it smells like some mathematician or programmer started to use the term incorrectly, and then it became de facto standard in those technical branches before awareness of the term reached a wider audience. Then perhaps Oxford et al just had to deal with it and go with the capital letter. Just speculation though. – user29079 Apr 17 '13 at 8:49
  • @Ludin, define "incorrectly". – Jeanne Pindar Apr 17 '13 at 11:08
  • I suppose Wictionary is the canonical reference. If they write Boolean there, then that's how it should be spelled, reason be damned. Long live the infallacy of Wikipedia! – Thomas Eding Apr 17 '13 at 15:05
  • @ThomasEding Yeah right... – user29079 Apr 17 '13 at 15:22
  • @JeannePindar Incorrectly is how you just spelled my name :) Apart from that, incorrectly as in inconsistent, see the link in the question: "shrapnel", "diesel", "saxophone", "baud", "ampere", "chauvinist", "nicotine". – user29079 Apr 17 '13 at 15:24