My dictionary says they are both cure/fix, so I am wondering what the difference is and how to use them?
Is it an active/passive difference, or transitive/intransitive? Or just a subtle nuance? I couldn't find a good example of usage.
I found this question, but it just refers to the different kanji, not the different words.
Thanks
治す is transitive.
傷を治す
to heal a woundほとんどの病気は薬を使わずに治すことができる。
Most ailments can be cured without medicine.
治る is intransitive.
風邪が治った
my cold got better傷が治らないので、私はまた病院に行った。
My wound did not heal, so I visited the hospital again.
治す takes a subject marked with を, meaning healing/fixing that thing, while 治る uses が and means the thing itself is fixed/healed.
transitive/intransitive difference.
風邪 を 治す。
I'll cure my cold.風邪 が 治る。
my cold will be cured.
It's almost exactly the same as the difference between 教わる and 教える, only in this case English uses different words: "learn" and "teach".
The other answers give the correct grammatical explanation, but I think it helps to see that this is not really a Japanese peculiarity, it's a curious fact about English that in very many cases the same verb is used for the entity receiving something and the entity giving the something.
In Japanese this distinction is shown by referring to 自動詞 ("self-acting" verbs) and 他動詞 ("other-acting" verbs). Many J dictionaries show this after the headword: for example, 新明解国語辞典, highly recommended, gives なおる【自五】 and なおす【他五】. Those single characters may tell you all you need to know.
