"Lay" is to physically place something somewhere.

"Lie" refers to the act of reclining or lying down.

You cannot phsically pick yourself up and PLACE yourself somewhere. You "lie" down; you "lay" an object somewhere.

--Roy, Literacy Volunteers in Buffalo, New York

Use "lay" when you act upon an object. I will "lay" the pillow on the bed. Use "lie" when you act upon yourself. I will "lie" down on the pillow. But be careful when using the word form as an irregular verb. Yesterday, after I came home from the soccer match, I "lay" [not "layed" or "laid"] down for a few hours.

--Daniel, USA

Lay – laid – laid: regular except for spelling. It means “to put something down, to place something”. It is something you do to something else. It is a transitive verb, which means it has an object.

Note the phrase to lay the table (= put plates, knives etc. on the table).

Lie – lay – lain: irregular; note the -ing-form: lying. It means “be down, be/be placed in a horizontal position”. It is an intransitive verb, which means it has no object.

Lie – lied – lied: regular. It means “say things that aren’t true”.

--Angelika Weichhart, Austria

There is a very firm rule, but there is also a notable exception when writing in past tense.

First, the rule: "to lay" is transitive and "to lie" is intransitive. Transitive verbs are used when the subject is acting on an object, and intransitive verbs are used when the subject is acting on or by itself.

If you're writing in future tense, you would write "I will lie down" (intransitive--the subject of the sentence, "I," is lying down), or "I will lay my pencil down" (transitive--the subject is acting on a thing, the pencil).

Now, the exception: the past tense of "to lie" is also "lay." (This is different from the past tense of "to lie" in the sense of "telling a falsehood," which is "lied").

So if you are describing a nap you took yesterday, you would write: "I lay down yesterday."

Incidentally, the past tense of "to lay" is "laid:" "I laid my pencil down yesterday."

A handout on the OWL site offers a few more examples and other tenses of "to lie:" check out owl.english.purdue.edu/handouts/print/esl/PDFs/eslirrverb.pdf . Good luck!

--Aaron Minnick, Columbus, OH

See Ernest Hemingway's excellent short story, "The Snows of Kilimanjaro," in which Harry, the dying protagonist, has his thoughts displayed in italics. I think the use of the italics makes for easier reading.

--Judy Henn, Technion Israel Institute of Technology, Israel

Shouldn't it be according to your style of writing? APA,MLA and others.

--Gerrie, Boca Raton, Florida -Florida Atlantic University