Hi Amit
RE: In a sense, every proper definition is a tautology (a triangle is a plane figure with three straight sides, is one example)

In what sense is your definition a tautology? If I am explaining geometry to students who (let’s say) don’t know what “triangle” means, and I give them your definition, am I simply repeating the same information twice and not telling them anything they don’t already know? They have learnt a new thing, have they not – what the word triangle means?

By contrast, if I say to someone “Every experience you are aware of is a conscious experience”, and I accept that “aware” and “conscious” mean much the same, I am in effect saying “Every experience you are conscious of is a conscious experience". That is a tautology. The listener is told nothing new.  Imagine a scientist addressing a group of his colleagues and saying: “Great news! I have discovered a new element! It’s called novium. I define it as novium”. His audience is likely to lose interest rather quickly, don’t you think?

DA