What is a lie?

A lie is when you know that what you’ve said is wrong, an example you know that you cannot lift 200kg but you say you can.

But if you say “I’ll be there in the morning” and you’re not because something happens between now and then, are you lying?

Then you have plausible deniability where you lie but not knowing that you are lying because you do not know that facts are different to what you have stated is that a lie?

Is it a lie when you say I’ll leave the office in 5 minutes and then write for another 15 before you look at the clock again, what is the defining truth in it, its knowing that you are going to do it, that answer if your intentions are to do it and you don’t, that’s not a lie that just not being able to.