(Re: Phoenix31's "I wonder if there is a difference between types of delusions or their severity" and the question of self-esteem's potential relationship to delusion. Sorry to not quote in proper format.)

It sounds like we might be talking about the word being used in a common vs medical sense. For instance, one can experience a delusion in a manic episode -- like believing that they can control the weather. Or that Abraham Lincoln is spying on them. (Like x123 points out, grandiosity or persecutory.)

Or, we could be talking about my mother. She's about as famous and accomplished as dryer lint. Yet she is always seeking to puff herself up -- going on about being in some "business womens' league" (she's an ordinary laborer). Or insisting she is a computer whiz, yet sending out things with viruses due to being oblivious of the need to update her anti-virus software.

Mind you, she's chock full of psychological problems. But I think the above examples are about self-esteem, yes? It would be said she's rather delusional about her abilities and social group. But they're the things of ordinary life, puffed up in an attempt to impress others or simply avoid admitting how utterly ordinary she is. A resumé of overstatement might be a good comparison.

She also believes that an old beat up violin stuffed in her closet is a real Stradivarius. It isn't even a fake, let alone a real one. I think we move into delusion in a more formal sense with that, don't you? It's preposterous, easily proven to be so, yet she's convinced. It goes way beyond resumé-fluffing. It's pathological.