Writers often confuse the verb pairs "lie" and "lay" and "sit" and "set."
"Lie" and "Lay"
The verb "lie" is an intransitive verb which means "to recline" or "to be situated". The present participle of "lie" is "lying," the past form is "lay" and the past participle is "lain":
The cup is lying on the floor.
The cat lay in the sun all morning.
The newspapers had lain on the verandah for two weeks before anyone noticed that Mr. Gilfillian had disappeared.
In each of these examples, the intransitive verb "lie" is used (in conjunction with an adverbial phrase) to describe the location of the subject.
The verb "lay" is a transitive verb which means "to place" or "to put." The present participle of "lay" is "laying," and both the past form and the past participle is "laid":
I was laying the cups and saucers on the table when I dropped one.
Jenkins laid the suspicious parcel on the commissioner's desk.
The supervisor had laid a cup of scalding coffee on the counter only moments before the bulldozer rammed into the construction office.
In each of these sentences, the transitive verb "lay" is used to describe the fact that someone had placed something somewhere.
Sit and Set
The verbs "sit" and "set" are also frequently confused. The intransitive verb "sit" means "to rest" or "to occupy a seat." The present participle is "sitting," and both the past part and the past participle are "sat."
Charlie will be surprised when he learns that he is sitting on a freshly painted bench.
We sat in the corridor outside the dean's office all afternoon.
The student delegate is persistent; they have sat in the excruciatingly uncomfortable chairs outside the dean's office for several hours.
In each of these sentences, the verb "sit" is used in conjunction with a adverbial phrase to describe the position of the subject.
The transitive verb "set" means "to place," "to put," or "to lay." The present participle of "set" is "setting," and both the past form and the past participle are "set":
The clockmaker was setting his tools on the bench when the hooligans came into his shop.
Germaine set plates and soup bowls on the table.
Once we had set the clock ahead an hour, we went to bed.
In each of these sentence, the verb "set" is used to describe the placing of an object in a specific place.