The difference between "lie" and "lay" can be quite confusing. Here's a simple breakdown:

• Lie is an intransitive verb, which means it does not require a direct object. You use "lie" when someone or something is reclining or resting on a surface by themselves. For example, "I want to lie down."
• Lay is a transitive verb, which means it requires a direct object. You use "lay" when you are placing something down. For example, "Please lay the book on the table."

To add to the confusion, the past tense of "lie" is "lay," and the past participle is "lain." So you would say, "Yesterday, I lay down for an hour," and "I have lain down every day this week."

The past tense of "lay" is "laid," and it remains the same for the past participle. For example, "I laid the book on the table yesterday," and "I have laid books on that shelf for years."

Remembering the difference can be tricky, but one tip is to remember that "lay" requires an object—something being placed—while "lie" does not¹².