I may be using the wrong term, but I understand the infinitive form of a verb in Japanese to be the form we add ~ます to. In the case of ichidan verbs, we take away the ~る and add ~ます、and for godan verbs we change the ending う-line to an い-line and add ~ます. Why then, is くださる not conjugated as くださります in infinitve form, and instead conjugated as くださいます? Additionally, why do we only use ください most of the time?

EDIT: To clarify, I'm interested both in the functional purpose of this, and any historical or cultural purpose of this if they exist. Thank you!


2 Answers 2


It is just because it is easier to pronounce. It is called イ音便.

This also happens in English like "I am" and "I'm."

But, since this change started around 8th century, now it is rather natural to say in イ音便 form.


くださる is a keigo verb. Keigo is the polite "language", and it's divided into:

Sonkei-go - Courteous language (it's not excessively polite). Kenjô-go - Humble language (used to talk about yourself or people next to you to your superiors. Teinei-go - Honorific language (used to talk about your interlocutor when he's superior than you).

Every kind of keigo has its own verbs. And some of them have a different conjugation. Don't worry they're only five:






They're conjugated the same as every godan verb, but the "り" which should be before "ます" is changed by an "い".

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