Translation guide
How to express that a skill or ability has declined due to lack of practice, or that a metal object has developed rust.
The speaker wants to say that their proficiency in something (language, sport, instrument, etc.) has worsened because they haven't used it in a while.
Literally 'one's arm dulls'. A very common and natural way to say a skill has become rusty. Used for practical skills, sports, arts, etc.
最近ピアノを弾いてないから、腕が鈍った。
I haven't played the piano lately, so I've gotten rusty.
Literally 'one's sense dulls'. Used when your intuition, feel, or sense for something has become less sharp.
The speaker is talking about a metal object that has become covered with rust due to exposure to moisture.
I haven't driven in a while, so my feel for it is rusty.
Literally 'one's arm falls'. Means one's skill has declined. Similar to 腕が鈍る but slightly more direct about a drop in ability.
練習しないと腕が落ちるよ。
If you don't practice, you'll get rusty.
Simply means 'become unskilled'. Less idiomatic than the above, but straightforward. Can sound a bit blunt.
毎日練習しないと、すぐに下手になる。
If you don't practice every day, you'll quickly get rusty.
The standard verb for 'to rust'. Used for iron, steel, etc.
この自転車は雨ざらしで錆びてしまった。
This bicycle got rusty from being left out in the rain.
Literally 'rust attaches'. Focuses on the state of having rust on it.
長い間使わなかった包丁に錆がついた。
The knife I hadn't used for a long time got rusty.