At one time Venerable Sāriputta and Venerable Mahākoṭṭhita were staying near Varanasi in the deer park at Isipatana. … Mahākoṭṭhita said to Sāriputta: “Reverend Sāriputta, they speak of this thing called ‘ignorance’. What is ignorance? And how is an ignoramus defined?”

“Reverend, it’s when an unlearned ordinary person doesn’t truly understand form, which is liable to originate … liable to vanish … liable to originate and vanish, as form which is liable to originate and vanish. They don’t truly understand feeling … perception … choices … consciousness, which is liable to originate … liable to vanish … liable to originate and vanish, as consciousness which is liable to originate and vanish. This is called ignorance. And this is how an ignoramus is defined.”

Linked Discourses 22.128 13. Ignorance Liable to Originate (3rd)

At one time Venerable Sāriputta and Venerable Mahākoṭṭhita were staying near Varanasi in the deer park at Isipatana. … Mahākoṭṭhita said to Sāriputta: “Reverend Sāriputta, they speak of this thing called ‘knowledge’. What is knowledge? And how is a knowing one defined?”