Someone once said "It's not a lie if you believe it".
I've said - a lie is the INTENT to deceive. A wrong answer on a test isn't a lie. It's just wrong.
Look it up. Any dictionary should define it thus - INTENT to deceive, either by admission or omission.
If you leave something OUT because it will get you in trouble - you're deceiving. It's a lie.
If you forgot because you're scatterbrained - not lying.
If you mention something innocuous - like, the event downtown is at 1pm and you said that BECAUSE YOU WANT THE HEARER TO MISS OUT - then you're lying.
But if you thought it was 1pm and found out you were wrong - then you're wrong. Not lying.
If you thought you took out the trash and say you did - mmmm - gray area. I always check when I am not sure.
When you are SO CERTAIN it's a quote from Shakespeare - and it's the Bible - and Shakespeare NEVER said it - you're just wrong. You're LYING when you KNOW it's false, but say it anyway.