Definition: Not valid; not true, correct, acceptable or appropriate.
Alright class, settle down, let’s take a peek, At “invalid,” a word that needs to be sleek! The dictionary tells us, clear and bright, It means something isn't quite right. “Not valid,” it states with grace, "Not true or correct in this space!" Think of a ticket, worn and old, Or a password that’s been left untold. It’s not accepted, doesn’t fit the key, An "invalid" thing – you plainly see! So ‘invalid’ means it's out of line, Not good enough, not truly fine. Do you understand? Any questions to share? Let’s make sure this concept is really there!