Verbs like お~になる, and なさる, and いらっしゃる all have casual and polite forms, but I’m not exactly sure when to use the polite and casual versions when speaking honorifically. It seems to me that if you are speaking to someone honorifically, sometimes you should use the polite versions, but because the casual versions are sometimes used im not sure. any clarification would help, thanks
I’ll let someone who has a better grasp of the language to offer more details but note that the “casual” form is just the short form that needs to be used in some constructions regardless of politeness.
For instance:
あなたの隣にいらっしゃるのはお嫁さんですか
Is the person next to you your wife?
Here the sentence is polite (ですか) but grammatically you can’t write “いらっしゃいますのは”, it has to be in the short form. This isn’t casual language, it’s just the short form as mandated by the construction.
I think another situation where you’d have a casual form of an honorific verb would be if you’re talking to someone you’re familiar with (and use the short form with) about a topic that requires the use of honorific language. Maybe something like a senior clerk talking to a junior about a client or something like that. I’m really not sure about this one however, so take it with a grain of salt.
As said above only the final verb denotes the politeness, whereas the vocabulary/grammar/context of the sentences as a whole denotes the formality. That means that it is very common for formal words to be used in their base ( ie. informal) form in the middle of a sentence.
Whether or not the final verb takes a politeness marker is either colloquial or up to the speaker. It is kinda strange but they are actually two different concepts and it can help parse certain trouble sentences.
For example 99% of modern people will say:
- よろしくお願いします。(Formal Polite)
but you could possible hear:
- よろしくお願いする。(Formal Impolite)
Both of these are ostensibly formal but the second is less polite.
Whereas:
- よろしく(ね) (Informal Neutral)
would be an informal counterpart.
The Key think is that politeness is not synonymous with formality.
This is the reason why “Plain form” is a better way to describe what some books call “Impolite form”. The reason is because the former is also used in formal settings since, as has been said, the politeness level is determined by the verb at the end of the phrase.
That said, you will encounter phrases that employ the “Masu form”, where the “Plain form” is commonly used, in order to make them sound even more polite. It might sound a bit stiff, depending on the situation.
Aside from grammatical constructions using the plain form, you might be in a situation where you’re talking to your friend (hence informally) about someone whom you should show respect to. In that case, you could use a respectful verb when talking about the person who isn’t there, but it wouldn’t make sense to use the polite form toward your friend. That’s a natural situation where plain-form honorifics could come into play.
Edit: I was tempted to add an example to drive the point home, but if you feel any uncertainty about applying this knowledge, I encourage you to create your own examples and post them here to really nail it in for yourself.
Edit 2: I highly recommend this video made by a Japanese native explaining the true function of 敬語. He speaks quite clearly, so I’d guess anyone who is N4 level or above should understand the majority of what he says, even without the English subs that are also generously provided, and it’s also the best explanation I’ve seen.