as far as i know, in japanese verbs are divided into two groups. One ends in a consonant and one in a vowel.

tor : stemform of toru. mi : stemform of miru.

those ending in a consonant are called godan-verbs, those in a vowel ichidan.

to attach further suffix to an ichidan-verb nothing is required but simply attach the suffix without any further change.

to attach further suffix to a godan-verb one has to attach an a,e,i,o or u before.

tor --Aeiou--> tora --suffix--> toranai. or: tor --aEiou--> tore --suffix--> toreba.

  1. am i right so for with respect to the grammar?
  2. is this rule without exceptions?

Yes, in fact, this is why they are called "Godan" 五段 ("five class") and "Ichidan" 一段 ("one class").

The five polite verbs can be considered an exception to your rule. They are considered "godan" but are conjugated a little differently.

  • いらっしゃる → いらっしゃいます　(Not いらっしゃります)
  • おっしゃる → おっしゃいます
  • なさる → なさいます
  • くださる → くださいます
  • ござる → ございます
  • 2
    I would say is more of "level" or "step" than "class", although this might be splitting hairs.
    – istrasci
    Oct 13 '14 at 17:58
  • 1
    Yes, literally. But it's really hard to translate it as such in this context. It's not as if the 5 "dans" are on any sort of hierarchy or scale, except their place in the rows of the Kana table. Oct 13 '14 at 18:08
