If someone says something that is not true, is it a lie even if (s)he genuinely believes it to be true?
If someone says something that they consciously believe to be true, but deep down they're just deceiving themselves, are they lying to anyone besides themselves?
If someone knowingly says something that isn't technically 100% factually accurate, but the spirit of what they've said is in line with reality, are they lying?
If someone says something that's technically 100% factually accurate, but the spirit of what they've said is not in line with reality, are they lying?
If someone omits information from something that they're telling you, are they lying? What if they honestly do not see how that information would be relevant? Or what if they honestly forgot all about the thing they didn't mention?