There is and there are...

Hello my friends…Here I am again…
When I have to explain the use of there is and there are I usually say that there is is for singular and uncountable things, and there are for plural, but for couple of times I have found myself tinking about it because sometimes in my concept it would be one and in the text I see the other,…am I wrong in my concept or there are different situations for the use of it.
tks a lot have a nice week everyone…
Elaine

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Sometimes notional accord with the predicate dominates, but your rule generally holds.
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ok thanks a lot…
Elaine