From Word Genius
“Lay” is a transitive verb. Transitive means that you have an object that is being acted upon. So “lay” means to set down or place something — an object — in a horizontal position. Here’s an example in the present tense: “I lay the book on the nightstand.” In this instance, the book is the object that is having something done to it.
“Lie” is an intransitive verb, meaning the object doesn’t need something else to put it down. Instead, the person or subject is doing the action. “Lie” means to stay at rest in a horizontal position, or to recline. An example of “lie” in present tense would be, “I feel the wind as I lie in my backyard on the grass.” In this example, the person is performing the action rather than having the action done to them.
So, in the present tense, the simplest way to determine which word to use is by looking at what is actually being reclined. If the reclining object is inanimate and/or requires someone to put it down, use “lay.” If the object is self-sufficient, such as a person, use “lie.” Quick memory tip: Only a person can lie on a bed and tell a lie.
“Lay” and “lie” in other tenses
Here’s a chart to help you understand how the two are used in different tenses.
Let’s tackle the past tense of each, since that’s where there’s the most opportunity to pick the wrong word.
I ____ my clothes out last night before I went to bed.
Which one is it — “lay” or “lie”? Here’s how to tell: Is something happening to an object? Yep! The clothes are being set out. That tells us that we need the verb “lay,” past tense “laid.”
I laid my clothes out last night before I went to bed.
Now, what about the past tense of “lie”?
I heard a noise coming from the basement as I ____ on the sofa watching a horror movie.
In this example, there is not a specific action being performed upon an object. Rather, the speaker (the subject) is doing the action. This means we need the past tense of “lie,” which (confusingly) is “lay.”
I heard a noise coming from the basement as I lay on the sofa watching a horror movie.
Confusing? Let’s see what CMOS has to say.
Usage and Grammar
Q. When is “lay” or “lie” used?
A. This question lay in our in-box for weeks, where we thought it might lie forever, and where it would have lain indefinitely had we not finally gotten around to answering it. Our first attempt to lay down a response wasn’t very good, so we laid it aside, but even if we’d laid down something worthwhile, we managed to lose it, so your question was still lying in our in-box before we finally succeeded in laying down the response you are reading right now.
As that first paragraph illustrates, the verb “to lie” is intransitive, so it doesn’t take an object; it describes a state of being rather than an action. It’s conjugated lie–lay–lain (for the present tense, past tense, and past participle). The present participle is “lying.”
The verb “to lay,” on the other hand, is transitive (with or without “down”), meaning that it takes an object (on which it acts). It’s conjugated lay–laid–laid. The present participle is “laying.”
So decide which one to use based on the presence or absence of an object. Then choose an appropriate tense and lie back—or lay yourself down if you’re not already prone—and enjoy the feeling that comes from knowing you’ve chosen your words with care.