is a 尊敬語（そんけいご） (honorific speech) verb which acknowledges and respects the actions of another (never the speaker). Like お～になる
has exactly the same meaning as する
can be utilized in any situation where する
would be used, as a direct replacement. It is a special-class verb, which means that it has some unique conjugation rules. In its casual form, it will conjugate in exactly the same way as a う-Verb
Are you going to work over the weekend also?
Please don't take this the wrong way.
Boss, where did you go to play golf last week?
If you are not with me on this, please let me know.
However, in the polite form, instead of ら changing to り (as would be expected of a う-Verb
), it will change to い instead.
What would you like to drink?
Did you forget anything?
Valued guest, what seems to be the issue?
He did not do anything to change the plan.
Although some Japanese speakers will use it, expressions like なさっていらっしゃる
are considered double keigo (なさる
is 尊敬語（そんけいご）, and いらっしゃる
is also 尊敬語（そんけいご）), and are technically incorrect. However, なさる
may be partnered with ます, which is simply 丁寧語（ていねいご） (polite speech).
The CEO is currently playing golf quite playingly. (Unnatural Japanese, with unnatural English to match!)
The CEO is currently playing golf. (Natural Japanese)
なさる is considered a little bit old fashioned in modern Japanese, and お～になる is the preferred form used by most native speakers.