1.
If you are mistaken about something, you are wrong about it.
I see I was mistaken about you...
You couldn't be more mistaken, Alex. You've utterly misread the situation.
= wrong
ADJ: v-link ADJ, oft ADJ about n
•
You use expressions such as if I'm not mistaken and unless I'm very much mistaken as a polite way of emphasizing the statement you are making, especially when you are confident that it is correct.
I think he wanted to marry her, if I am not mistaken...
Unless I'm mistaken, he didn't specify what time.
PHRASE: PHR with cl [emphasis]
2.
A mistaken belief or opinion is incorrect.
...a limited understanding of addiction and mistaken beliefs about how it can be overcome.
ADJ: ADJ n
• mistakenly
He says they mistakenly believed the standard licenses they held were sufficient.
ADV: ADV with v