lay/lie

Definition 
These two verbs are frequently confused, largely because lay is the past tense of lie as well as a verb in its own right. Lay means "put down" (lay a carpet, lay a body on the floor) and, as a transitive verb, always has an object (hens lay eggs). Lie means "rest" (lie on the bed; lie down on the grass) and, as an intransitive verb, does not have an object. Further confusion can arise with lie because it also has the meaning "tell an untruth," although its past tense is not the same (I lay on the couch; he lied through his teeth).