〜なければなりません

みんなさま、もう"~なければなりません”はラブで２５６かい話しましたか。とてもむずかしいですね。

すみませんが、このポストは英語で書かなければなりません。

I'm sure that a lot of my fellow Japanese students when encountering the slithery "~nakerebanarimasen" like me had the suspicion that there was an idiom or grammatical something-something at play.

なりません　＞　なります　＞　なる　＞　成る

This verb according to my dictionary means "to be, exist, become, consist of". It is the last verb of a list that establishes the sequential order of actions. The ending "ba" makes the verb or adjective conditional, and "nai" we know is negation. With this in mind, saying "私はたべなければなりません" means something like "If I don't eat, I cease to be". おもしろいね。It sounds a little drastic when translated literally, but this phrase captures the meaning of 'must' well. English has phrases that make use of hyperbole and litotes all the time, too (e.g. "I need to eat or I'll die a thousand deaths").

Sorry, this phrase has been giving me trouble so I thought it would be fun to share the results of my minimal research. Knowing a little more about what is going on doesn't make it easier to say, but oh well. It is also interesting to know that Japanese and English both have a strong notion of a double negative, which is relatively uncommon among languages.