IPA: /ɪˈrɒnɪəsli/
KK: /ɪˈroʊniəsli/
In a way that is wrong or incorrect.
She erroneously believed that the meeting was at 10 AM instead of 2 PM.
Erroneously → It is formed from "erroneous" (from Latin "erroneus", meaning wandering or straying) and the suffix "-ly" (meaning in a manner of). The word "erroneously" means in a manner that is straying from the truth or correctness.
Think of 'erroneous' meaning straying from the truth, and remember that 'erroneously' means doing something in a way that is incorrect.