Can someone explain to me in a way I can understand how it is that you can use some kanji in place of other kanji? Maybe I’m not expressing that right, but there are times when two (or more?) kanji can be used with the same meaning and reading. Why is that? How can you figure out which to use? For example, with 斉/等?
For your specific example, I have only seen the former used for ひとしい. They don’t share any other readings as far as I can see. A quick google search suggests that 等しい・均しい・斉しい all share the same reading. Seem to have the same meaning, but you can do more Googling.
In general, there’s some sets like the one above which have the exact same meaning but have two or more Kanji that are read that way. There’s basically always a “most common” way to write it, and you’lll find other versions in novels etc. where they want to be more fancy or something.
There are other cases where the different Kanji actually provide more context or nuance. For example 匂い・臭いare both read におい and both mean smell. However, the former is for good/neutral smells, and the former is for stinky smells.
Because that’s how the language evolved and some Kanji fell out of favor but still hold that old reading as a possibility etc. Or they actually have to different meanings
Case by case. Look into the meaning differences on a Japanese dictionary / blog post etc. Tons of people who make it their life’s work to write these kinds of articles explaining differences in Kanji meanings etc. Japanese people also struggle with this btw. By colleague the other day was wondering which Kanji to use for guarantee. 保証 or 保障
EDIT: here’s an interesting page on the many versions of うたう. https://違いは.net/archives/2284.html
That’s an awesome answer. Thank you very much.
Here’s an article (well, an archive of a blog post) written by a native Japanese speaker addressing this issue. On that note I suggest going through the whole blog, it has lots of great insight (and all posts are posted in both English and Japanese):