質問: In Genki II (second ed.), page 168 we are given polite forms of some verbs, among them する with なさる. They have also written that some of them have irregular conjugations in long forms, among them なさる, which becomes なさいます. However, in tangorin.com the conjugation table says なさります while Jisho.org recognizes both as forms of なさる. At the same when I type なさります or なさいます into google.com I get about 900 000 or 600 000 results respectively. Are both forms correct? Or is one of them just a common mistake?
回答: They are both OK. なさります is the original, but り sometimes changes to い. This is called イ音便{おんびん}. イ音便 なさいます なさります