Japanese verbs can conjugate to express a variety of meanings, including whether a verb is in the present or past, whether it's positive or negative, and more.
The next group of verbs we'll look at is ichidan verbs, which include 見る (mi ru ), "to see," 起きる (oki ru ), "to wake up," 開ける (ake ru ), "to open," and 食べる (tabe ru ), "to eat."
The patterns of conjugations for godan verbs in the て form, the past tense suffix 〜た, and some other forms that use 〜た like 〜たり and 〜たら, can be explained by a concept in Japanese linguistics called 音便, which refers to changes in pronunciation that occur to make a word easier to say.
The conjugations of 買う, which end in う, can seem like exceptions because they use the /w/ sound, but these exceptions can be explained by the historical context of the sound drift.
Godan verbs, also known as う -verbs, Group I verbs, and consonant-root verbs, can be identified by their endings in the plain/dictionary form, which end in a character on the う -line of the hiragana chart.
Ancient Japanese speakers decided that some conjugations that begin with a /t/ sound, like the て form, were too difficult/not pleasing to pronounce with certain verb roots.
Instead of pronouncing these sounds, it was deemed easier/more pleasing to drop them before conjugations that start with a /t/ sound, and to add in a double consonant small っ instead.
Ancient Japanese speakers felt that pronouncing these sounds before /t/ conjugations was too difficult, and so they blended them together by dropping the verb stem ending sound, replacing it with ん , and transforming the /t/ to a /d/.