I found this sentence in Longman dictionary:
The crux of the problem lay in the lack of equipment.
I think it should be "lays" instead of "lay", but even when I googled, I noticed there are more results for "lay" than are for "lays" in this context. Could you please explain which one is correct?
The correct answer for past tense is 'lay', as Longman tells you. You could use 'lies' as a correct alternative for the present tense.
Two irregular verbs that are often confused:
lay laid laid - German: leg-en legte gelegt
lie lay lain - German: lieg-en lag gelegen
You can lie in bed. You can lay a child in the bed.
