Sound changes are at the heart of another verb conjugation mystery — the strange patterns we see with godan verbs in the て form, the past tense suffix 〜た, and some other forms that use 〜た like 〜たり and 〜たら. If you're not familiar with these forms, then I recommend coming back to this page later when you're learning them and are wondering why the conjugations are so weird. If you're here because you're ready to dig into the why, then read on!
There is a concept in Japanese linguistics called <ruby style="box-sizing: inherit;">音便<rt style="box-sizing: inherit; font-size: 0.7rem;">おんびん</rt></ruby>, which refers to changes in pronunciation that occur to make a word easier to say. If you look at the kanji, you'll see 音便 is made up of "sound" and "convenience", which makes sense because it refers to making difficult-to-say words easier on the tongue. An example of this from English is pronouncing "want to" as "wanna" or "a lot of" as "alotta."
To really get how 音便 applies to verb conjugations, we're going to have to revisit some concepts. First is the idea of a verb root. This is the part of the verb that doesn't change when the verb is conjugated. However, 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. Out of this, three unique conjugation patterns that deviate from what you would expect were born:
- Double Consonant: when small っ pops up in a conjugation
- Assimilation: when two sounds blend together into ん
- Consonant Removal: when a consonant disappears
Don't worry, we're about to dive into examples of each, and we'll use the て form to illustrate!
DOUBLE CONSONANT WITH SMALL っ
The double consonant (small っ) is used when a verb root ends in /w/, /t/, or /r/. Instead of pronouncing these sounds, it was deemed easier/more pleasing to drop them before conjugations that starts with a /t/ sound, and to add in a double consonant small っ instead:
If you're scratching your head about /w/, scroll up and re-read the section above this one. In short though, verbs like 買う used to be pronounced /kawu/, so the root was kaw. Even though the /w/ is gone in Modern Japanese, it still affects how 音便 developed for /t/ conjugations like the て form.
ASSIMILATION WITH ん
The ん character is used when a verb stem ends in /m/, /n/, or /b/. 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/:
CONSONANT REMOVAL
When a verb root ends in /k/ or /g/, the consonant was removed completely, but the vowel remained. If the verb root ended in /k/, the verb ending would be attached with a /t/ sound. However, if the verb root ended in a /g/, the verb ending would be attached with a /d/ sound:
Remember, it's not important to memorize this information — this is here purely for your info, and so that you can get all the answers you need to your burning questions about Japanese grammar. Honestly, this will all become second nature with enough practice.
I guess: 以上五段动词变成 て型，原本的变化规则是：左移一列，+て。在音便规则的作用下，才成了这样较为复杂的规则。仅是猜的
