I was wondering whether there is a formal rule for or against substituting 'all' for 'both'?

We all know the difference between 'all' and 'both', but look at this question from ELL:


Here there are answers to the effect that both shall always refer to 2 things, and all can refer to more than one -- is that definition of 'all' widely accepted, and if it thus overlaps with 'both', can 'all' substitute for 'both' at least in certain cases?

Example 1 (2 is specified) :

he has 2 shirts -- both of them are white

he has 2 shirts; all of them are white

Example 2 (2 is implied) :

He crashed his bike. Both the wheels were smashed.

He crashed his bike. ALL the wheels were smashed.

I know that 'both' sounds better whetever clearly applicable, but can 'all' ever substitute for 'both', or is there a clear grammatical rule / convention that "thou shalt not use 'all' wherever 'both' is applicable?"

  • "How y'all doin'?"
    – Hot Licks
    May 19, 2017 at 0:35
  • If it's not important that there are precisely two, and if it's not necessary to mention this fact in every sentence, then all covers the territory from zero on up. May 19, 2017 at 0:39
  • @Hot Licks thanks, that's one way to refer to 2 people, right! May 19, 2017 at 0:40
  • @John Lawler Thank you, but I am referring to situations where 'two' is implicitly known. Specifically I should like to know whether 'both' is to be preferred to 'all' wherever applicable? May 19, 2017 at 0:42
  • 2
    Both means two, and it strictly refers to two - not less and not more. Suppose, you have only two shirts and you haven't explicitly mentioned that number. Then you can say all your shirts. But once you have mentioned two shirts, you have to refer to them as both in positive sentences and neither in negative sentences. If you say my bike got crashed and all the wheels were smashed, there is an implication that you had a 'three-wheeler' bike! Normally a bike implies a two-wheeler vehicle, so the use of both the wheels is unambiguous as well as correct. May 19, 2017 at 0:52

2 Answers 2


If the set has a known number of objects and that number is known to be two, you should use "both". Using "all" will sound unnatural, and it may even cause confusion (by implying you are talking about something else).

When in doubt, avoid ambiguity.

  • Thank you! That's what I thought. I would appreciate it even more if you could find me some rule that explicitly says so, which would completely answer my question. May 19, 2017 at 0:44
  • English doesn't have a formal governing body, so I'm not going to be able to find you an official rule. May 19, 2017 at 0:57
  • Official rule is not needed. I HAVE not even found a ruling in a style guide! Please note: I have down- voted your answer by mistake. Kindly make some minor edit in your answer (any small letter or punctuation) so that the software will allow me to correct the error. May 19, 2017 at 1:00
  • Well I think any style guide would support the notion of reducing ambiguity. May 19, 2017 at 1:07
  • VERY TRUE. It is probably to be understood as self-evident, and therefore not specified. Thanks a lot for your clear answer, and don't forget to make that minor edit! May 19, 2017 at 1:09

All can indeed be used to refer to everything in a set containing two elements.

It is even possible to say "all two", for example:

I felt bad for taking all two chicken legs and not leaving anything for you, but I was just so hungry.

Yes, it might sound a little weird, but there's no rule against it, and if you're the sort of person who likes logical preciseness, you might be more likely to use "all" in place of "both" in certain circumstances.

  • It is certainly a very nice example and very appropriate within its own context, when 'two' is 'all' there is -- thanks a lot for adding a fresh dimension! May 19, 2017 at 4:46
  • It does sound weird. This is about language, not about logic. No one talks like that. (By the same "logic", you could also say "all zero people talk like that".) May 19, 2017 at 8:20
  • @michael.hor257k - I'm looking at the intersection of math (logic) and language. But I promise not to try to force you to do that! May 19, 2017 at 18:14

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