What are the the past tense and the past participle of lie?

Answer 1

The past tense and the past participle of the verb 'to lie', meaning 'to tell an untruth', are both 'lied':

'I lied when I told you I loved you.'

'I have lied to you ever since we met.'

The past tense of the verb 'to lie', meaning 'to be situated', is 'lay', and the past participle is 'lain':

'I lay on a towel on the beach in the sun.'

'I have lain there every day this week.'

Answer 2

The past tense of "lie" is "lay" and the past participle is "lain."