Lay is a transitive verb that means "to place or put." Lie is an intransitive verb meaning "to rest on a surface". Both verbs are irregular.
Now I always lay my glasses next to my
computer. [present tense]
My glasses always lie next to my computer. [present
tense]
Twice last week I laid my glasses on the
laboratory bench. [past tense]
Twice last week my glasses lay on the
laboratory bench. [past tense]
I forgot where I had laid my glasses.
[past participle]
I found that my glasses had lain on the
laboratory bench all day. [past participle]
