In terms of words that are commonly confused, the difference between "lie" and "lay" is particularly troublesome as both meaning and conjugation of tenses can be confused. To learn the difference between the verbs, it is important to distinguish between the action you perform for yourself and the action you perform upon another object.
Present Tense of Lay
As a transitive verb, "lay" is performed by a subject upon something else, which is called the object of the verb. A person, the subject of a sentence, could lay a book on something, where the book would serve as the object of the verb lay. For example, Julie lay the food on table. Because Julie is placing another object, you would use the word "lay" to describe her action.
Present Tense of Lie
The verb "lie" is an intransitive verb, which means that it does not need an object It is something you can do to yourself and refers to the idea of reclining upon something. For example, Julie lie on the bed after a long day. In this example, Julie is the subject and the action she performs is to lie, or rest, upon the bed.
Other Forms of Lay
In addition to the present tense of lay, it is important to be aware of other forms of the verb and its use as a transitive verb. The past tense is "laid," past participle is "was laid," future tense is "will lay," and the present participle is "is laying." In all forms of this verb, a subject performs the action and there must be an object that receives the action. For example, in the past tense, Julia laid the book on the table, where Julia is the subject and she performed the action upon a book. Additionally, "Julia will lay the book" or "is laying the book" are also appropriate constructions. When using the past participle, the object of the verb comes first and "the book was laid on the table."
Other Forms of Lie
Conjugations of "lie" require some additional thought as they overlap with "lay" or remain in the same format as the present tense. The past tense is "lie," the past participle is "has lain," the future tense is "will lie" and the present participle is "is lying." In all forms of the verb, the action is still performed solely by the subject and does not require an object. For example, in the past tense, John lie on the bed after work. Additionally, John "will lie" or "is lying" also are correct conjugations. In the case of the past participle, "John has lain on the bed every day after work" indicates that the action was performed multiple times in the past.