Weird Sentence and Counter?

Okay so I tried writing "tomorrow is the monthly test" in Japanese.
So I wrote "明日は毎月の試験です。"

But it was corrected to 明日は月に一度の試験(の日)です。

I don't understand why に is after 月, I don't understand 一度の(I know it's a counter), and I don't understand why の日 is there.

Help please

毎月 まいげつ means every month. So in your original sentence it said tomorrow is every month's exam which while effective in communicating, it does not sound natural.

Also 毎月 is a Chinese compound consisting of the modifier 毎 and noun 月. But it is imported whole as a whole word in Japanese. Usually these things have very restricted usage in Japanese as there are always Japanese native alternatives for these basic ideas which is preferred as in this case. In Chinese 毎月 would have no such restrictions.

月に means monthly. Think of に as the ly in monthly (for the purpose of understanding this example). You can also say 週に to mean weekly. 一日に for daily

However unlike English you have to follow these expressions with how many times in a month or week or day as by themselves they don't imply once or twice or however many unlike in English so that's what the 一度 is for.

月に一回 once a month or monthly
月に三回 3 times a month
週に六回 6 times a week
Etc

There are alternatives.
月毎に つきごとに
一ヶ月に付き いっかげつにつき etc

Welcome to the world of Japanese where there are a million ways to say the same thing.

As for the の日 part. It would sound more natural to say tomorrow is the day of the monthly test. It is in brackets as Japanese is quite forgiving in leaving out words when they are implied but as an independent sentence it is clearer if you leave it in.

Sorry for nitpicking, but まいげつ is not incorrect but まいつき is more common.;-)

I think に is more close to "per / every" here, since に can be used not only for "~time(s) a month/week/day", as in 二週間に一度 "once every two weeks", 三ヶ月に四度 "four times every three months".

Another option for "monthly" is 月例 (e.g. 明日は月例テストの日です。). Interestingly, this 例 can be used only for month, i.e., 日例, 週例 or 年例 are all not used.

Morphling said:

As for the の日 part. It would sound more natural to say tomorrow is the day of the monthly test. It is in brackets as Japanese is quite forgiving in leaving out words when they are implied but as an independent sentence it is clearer if you leave it in.

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Yeah, this reminds me a famous examble so-called うなぎ文 (僕はウナギだ can mean "A bowl of rice topped with grilled eel(うな丼), please", not "I'm an eel", in a specific context.).

うなぎ
(all in Japanese)

Thanks all of you!!

Toritoribe said:

うなぎ
(all in Japanese)

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I just read this again, and nearly replied with the same thing I did last time you posted the link. I guess my impression of it still hasn't changed. haha