My Japanese is rusty

Question

While it sounds perfectly alright when said in English, as in "My English is rusty", is there an equivalent in Japanese language?

I have used this line before when I said "私の日本語は錆びている" and "私の日本語は錆びっちゃっている" but only to be met with silence from the other person. So I wondered if I had said something wrong or awkward?

Or does it makes sense to say it as 私の英語は錆びついている. But is it even natural for Japanese to say that?

Therefore, my question is, can it be directly translated into Japanese or is there an equivalent to that line of sentence when said in Japanese?

Answer 1

This is a classic example of how direct translation rarely works between English and Japanese.

When I, a Japanese-speaker, learned years ago that in English they say "My [language name] is rusty.", it took me by surprise because in Japanese, 「錆{さ}びる = "to get rusty"」 is rarely used outside of a context regarding metals.

A far more common and natural word choice would be:

「下手{へた}になる」

Use that and every single Japanese-speaker would instantly understand what you are trying to convey.

If you used 「錆びる」, regardless of the verb form, only a highly limited number of native Japanese-speakers would understand it immediately. You would often end up having to utter an extra long sentence or two trying to rephrase what you just said.

Frankly, those who would at once understand any of your three sentences would be the ones who speak a good amount of English.

So, you could say:

「日本語が下手になってしまいました。」,

「日本語が下手になりました。」, etc.

Finally, you do not need to use the personal pronoun 「私」 as we will surely know, from the context/situation, exactly whose Japanese proficiency you are talking about.

Answer 2

"私の日本語は錆びている" （← unnatural)

"私の日本語は錆びついている" （← natural)

"私の日本語は錆びっちゃっている" (wrong)

"私の日本語は錆びちゃっている" (OK)

"私の日本語は錆びついちゃっている" （OK)

It is natural to use that expression in Japanese, which is popular and widely accepted.

I personally guess, however, the etiology of the expression is from English. I don't think that expression existed before Meiji Era. It was imported as 翻訳口調（the direct-translation style).

Answer 3

Adding to 下手になる mentioned by another poster, I think you could also use phrases such as:

「（[使]{つか}わないから）[忘]{わす}れてしまった。」
「[腕]{うで}が / ～～[力]{りょく}が　[鈍]{にぶ}った。」
「[腕]{うで}が / ～～[力]{りょく}が　[落]{お}ちた。」

as in:

「英語は、長い間使っていないのでずいぶん忘れてしまっています。」
「英語力がすっかり落ちてしまいました。」

or maybe...

「英語を使う機会がないので、うまく話せなくなってしまいました。」

Answer 4

I'm not a native speaker, but I've used 鈍くなった（にぶくなった） in the past. 「最近、僕の日本語は鈍くなったんです」。

Answer 5

Here are some good ways to translate "My Japanese is rusty":

「日本語力が落ちた」

「日本語がでてこない」　

「腕が鈍った（なまった）」