I'm studying for the N4 of the JLPT and in the 尊敬語 lesson is the verb おっしゃる
おっしゃる is the respectful form of 言う. When in the textbook they change the verb to the ます形 it changes in a way that I can not understand.
How I understand it should be
おっしゃる ► Ends in "る" so the "い" sound of that character is "り" ► おっしゃり ► and then we add the ます ► おっしゃります
How it is in the textbook:
おっしゃる ► おっしゃいます
The same happens with
くださる ► くださいます
なさる ► なさいます
いらっしゃる ► いらっしゃいます
Does someone knows why it is like this?