‘Laid’ or ‘lain’?
People are often perplexed about this group of words. The important thing to remember is that there are two quite separate verbs involved.
Lay is the present tense of a verb whose basic meaning is ‘place something in a more or less horizontal position’, with the past tense and participle laid.
Lay is also the past tense of the verb lie (‘assume a horizontal or resting position’); while lain is the past participle.
So the proper use is:
Please lay it on the floor.
Go and lie down.
She laid the book on the desk.
She went and lay down.
They had laid it on the floor.
The body had lain in the field for some time.
Read more about ‘laid’ and ‘lain’ on the Oxford Dictionaries blog.
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