全く vs 全然 (formal / casual)


What is the difference between 全く vs 全然? Is there a preference between using
全く or 全然 in essay writing?

[Is this true](https://twitter.com/akokitamura/status/567154059694469120):

> 全部 (zenbu) all [casual]  
> 全て (subete) all [formal]
>
>   * 全然〜ない (zenzen nai) not 〜 at all [casual]
>   * 全く〜ない (mattaku nai) not 〜 at all [formal]
>




I think you had better use 全{まった}く than 全然{ぜんぜん} in your essay because 全然
carries a bit stronger emotional overtones than 全く does. 全然 probably gives an
informal, easy, friendly, or familiar impression.

It's no problem for you to use 全然 in conversation or in E-mail to your friend,
however, it isn't appropriate for a serious or polite essay.

