I was taught that the pattern ‘If you should’ is rather formal and is used in the case when a speaker supposes an event (condition) to be very unlikely, just a chance possibility.
If your should see Ann, please ask her to phone me tomorrow.
OK.
My question is:
Is If you should equivalent (in the above sense) to If you happen or the latter still means ‘more possible’? Or the latter is exactly the same, but just a bit less formal?
Hi Tamara,
You asked:
I would say they are about the same - both indicating a tentative request. [i]You can also say: If you should happen to meet …
If by chance you meet …
On the off chance that you meet [/i]…
Alan
Hi Tamara
In American English, “If you happen to see” would be a much more typical expression. “If you should see” sounds fairly formal in AmE.
I’m not sure that I would think of “happen to” strictly as being used for “very unlikely” situations, though. It might be used in a situation where the degree of likelihood is simply unknown.
Amy
all have the same meaning and are employed when there is a slight possibility of something happening. The last one is the most commonly used of the three.
Hi all
Oh yes… I’ve just forgotten it…
But I’ll never dare to use the pattern aloud 
, as for me it sounds frightfully formal and bookish.
But you all gave me the ways how to avoid using if-should for ‘highly unlikely’ cases. I just don’t like the pattern – with no any reason.
Thanks to you all!
Tamara