Verbs with ending [ます] to [く]

Question

I know a verb ending in 「ます」 has a 「く」form. For example: いきます-> いく. Can you do this with any verb, or are there some rules?

Answer 1

First, you have it backwards: いく is the plain form of the verb, and いきます is a form that you create by following a rule.

The plain form happens to have く in this case, but that is not at all a rule. The plain forms of verbs end with a う sound, but it can be any う-row kana. (This is not "a consonant followed by う"; in the Japanese way of thinking about it, the consonants don't really exist separately, and a sound like く is indivisible.)

The rule that you first form a "stem" to which ます can be attached, and then you attach it. For [一段]{いちだん} verbs (this is some of the verbs that end in る), to make the stem, you simply drop the る. For [五段]{ごだん} verbs (this is almost everything else), the last kana must shift to the corresponding い-row kana: so う becomes い, く becomes き, す becomes し, etc. And yes, since some verbs ending in る are 五段, in this case it changes to り.

Thus: [行]{い}く -> 行き + ます -> 行きます. [見]{み}る -> 見 + ます -> 見ます. [頑張]{がんば}る -> 頑張り + ます -> 頑張ります.

This ます form is considered to add politeness. Japanese study programs often teach it first, on the theory that it's better for students to be accidentally too polite than accidentally too casual. However, some instructors oppose this practice, believing that it impairs ready understanding of the Japanese verb conjugation system.