Intermediate (B1)
IPA: /ˌʌnɪnˈtɛnʃənəli/
KK: /ʌnɪnˈtɛnʃənəli/
Definition
In a way that is not planned or intended; by accident.
Example
She unintentionally hurt his feelings with her comment.
Conversation

I think I might have offended her unintentionally during our conversation.

I just mentioned her project, but I didn't mean to criticize it at all.

That happens sometimes; I'm sure she'll understand it was an accident.
Synonyms & Antonyms
Synonyms
accidentally
inadvertently
unwittingly
Antonyms
intentionally
deliberately
purposely
Root Explanation
Unintentionally → It is formed from "un-" (meaning not), "intent" (from Latin "intentus", meaning stretched out or aimed at), and "-ally" (meaning in a manner). The word "unintentionally" means not done with intention or purpose.
Memory Tip
Think of 'not' ('un-') doing something 'aimed at' ('intent') — that's why unintentionally means something done without purpose.
Visually Confused Words
intentionally
internationally
intensionally
intentional
unconventionally
intentionality
punitionally
intestinally