While reading this old question, I began wondering what the て-form without the て (i.e. 書いて→書い、読んで→読ん、行って→行っ) is called in Japanese. Wikipedia calls it 2つ目の連用形. Some other places call it 連用形の促音便形 or 連用形の撥音便形. I'm curious as to what teachers call this when they teach to kids as well as what it's called when discussed in research etc.
A related question is: 書かない→書か、書こう→書こ are both considered 未然形. Is there any way of disambiguating the two other than Wikipedia's 2つ目の未然形?