Page 109 - JAPN1002

#五ぺカゃだぱ& (five-step verbs)
(Verbs whose forms change depending on the context)
In contrast to one-step verbs, five-step verbs change in five ways: one verb can have a-step, i-step, u-step, e-step, and o-step syllables depending on the grammatical context. Here we only look at three changes: a-step, i-step, u-step.
The dictionary forms of five-step verbs all end in u-step syllables (ィ\ど\\び, etc.) as you can check in the chart below. The negative forms each have corresponding a-step syllables before やぞ. For example, the dictionary form 分づィ ends in ィ, and its negative form has ァ before やぞ (分づィ−分づァやぞ). Since ァ and ィ belong to the same ァ...ア...ィ... イ...ゥ line in the Hiragana chart, ァ is said to be the corresponding a-step syllable of ィ. Similarly, ど corresponds to づ (書ど−書づやぞ) and corresponds to (読−読 やぞ), etc. There is only one exception to this: in the case of だ, the corresponding a-step would have been ぜ, but in fact it is ェ as in ほてだ−ほてェやぞ, 買だ−買ェやぞ.
As for the stem form (the form before び), it is consistently in i-step syllables.
In summary, here are the three rules:
Use だ-step syllables for non-past positive forms (=dictionary forms).
Use ぜ-step syllables for non-past negative forms. *(but use ェ for だ ending verbs) Use ぞ-step syllables for stems.
Non-past positive
do
Non-past negative
do not do
ぜ-step 分づァ...やぞ てァ...やぞ もァ...やぞ づづァ...やぞ ぞァ...やぞ 作ァ...やぞ 帰ァ...やぞ やァ...やぞ
Stem
(= the form before ×び)
ぞ-step 分づア≧び∞ てア≧び∞ もア≧び∞ づづア≧び∞ ぞア≧び∞ 作ア≧び∞ 帰ア≧び∞ やア≧び∞
Meaning
understand turn
stay over take (time) need
make
return, go home become
だ-step 分づィ てィ もィ づづィ
ぞィ 作ィ 帰ィ やィ
Lesson 11A Page 330