What it means
全く〇〇ない emphasizes a complete negative result, meaning “not at all” or “entirely not.” It is placed before a predicate in a negative form and is commonly used when the speaker strongly denies a state, action, or quality. The predicate may be a verb, an i-adjective, a na-adjective, or a noun-based predicate. In polite speech, the corresponding endings are usually ません or ではありません rather than ない or ではない.
Usage note
全く can also mean “completely” in affirmative expressions, so its meaning depends on the predicate and context. With a negative predicate, it normally means “not at all,” while 全然 is a more casual alternative with a similar meaning.
How to use it
彼は全く専門家ではありません。
He is not an expert at all.
この部屋は全く静かではありません。
This room is not quiet at all.
この説明は全く分かりやすくありません。
This explanation is not easy to understand at all.
その問題は全く分かりません。
I do not understand that problem at all.
彼は全く専門家ではない。
He is not an expert at all.
この部屋は全く静かではない。
This room is not quiet at all.
この説明は全く分かりやすくない。
This explanation is not easy to understand at all.
その問題は全く分からない。
I do not understand that problem at all.