なさるTo do (Honorific)

なさる is an honorific language verb which acknowledges and respects the actions of another (never the speaker). Like お～になる, なさる has exactly the same meaning as する.

なさる 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.

However, in the polite form, instead of る changing to り (as would be expected of a う-Verb), it will change to い instead.

Caution

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 honorific language, and いらっしゃる is also honorific language), and are technically incorrect. However, なさる may be partnered with ます, which is simply polite speech.

Fun Fact

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.