I've noticed that sometimes people use 'should' instead of 'if'. But if you replace the word 'should' by an 'if', it still makes sense.

For example:

'Your mission, should you choose to accept it'


'Your mission, if you choose to accept it'

Another example:

'You must evacuate if there is a fire'


'You must evacuate should there be a fire'

Are they always interchangable?


2 Answers 2


You can tell by your second example pair there is something different.

You must evacuate if there is a fire.
You must evacuate should there be a fire.

The word should forced you into subjunctive mood, should there be. It would not be wrong to say if there be, but many folks are not used to hearing the subjunctive in that context. (They might even consider you wrong or even "backward".) The point is, modern English did not force the subjunctive with if but it did with should. I am not sure why this is the case, but it could be there is a greater air of uncertainty with should -- sort of your anticipation of the possibility along with the possibility itself.

Also consider how moving the word should alters a sentence.

  1. Go to the store and buy some milk.
  2. You should go to the store and buy some milk.
  3. Should you go to the store, buy some milk.
  4. If you go to the store, buy some milk.

The transition is from a command, to a suggestion, to a conditional suggestion, to a conditional command. With #3 it as almost as if the Should supplied its own ", okay?" at the end. The If in #4 does not do that; it is just a dry, logical if..then construct.

  • I have never heard of if there be. Can you give examples from grammar books? Mar 24, 2017 at 6:05
  • @SovereignSun It is a little late, but one example is a 2015 movie -- en.wikipedia.org/wiki/If_There_Be_Thorns_(film) . In my experience, many black folks who speak American English preserve the subjunctive.while most white folks have thrown it away. Personally I think the subjunctive sounds better. // "Were there to be" is perfectly fine as well.
    – RichF
    Jan 14, 2021 at 16:38

If is more like being just a conditional as in if this occurs, while should is more like being forced in the condition. Like Should condition be forced. That's what I perceive.

You must log in to answer this question.

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