Which one is correct?
- I forgot about my password.
- I forgot my password.
(Meaning I forgot what my password is.)
Thanks a lot.
To forget about your password means you no longer know you that have a password. "Forget about" usually means the entire phenomenon has disappeared from your memory, but it can be quite subtle. The phrase "I forgot about dinner" would suggest that there were specific plans for dinner, but the speaker forgot them. It would not suggest that the speaker forgot that there is a nighttime meal called "dinner."
In the case of any item which requires memorization, if you are unable to recall the details of the item, you "forgot" it; if you forgot that you had the item, you "forgot about" it.
"Forget about" might also imply uncertainty about some other aspect of a thing. For example, "I forgot my PIN" means "I don't remember the numbers that make up my PIN." On the other hand, "I forgot about my PIN" sounds like an unfinished thought. What did the speaker forget about their PIN? Do they not remember they had one? Were they waiting for their PIN to be mailed to them and had forgotten it was coming? Were they supposed to change it for some reason but forgot to do so?