(A continuation of a discussion from Human Japanese Intermediate. Please note that the Japanese examples in this web appendix article are not linked to sound files.)
A moment ago we were discussing that based on the -masu form alone, it is unfortunately impossible to know for certainty what the dictionary form is. However, if you know the -masu form and the -te form, you’re homefree. Fortunately, that’s how we learned verbs in Human Japanese Volume 1, so let me show you how you can work back to the dictionary form without memorizing anything more.
Here’s the strategy. We’ll start with the -masu form and imagine the possible verbs that could conjugate to it. Let’s try this with the verb oyogimasu, “to swim.”
We can imagine two possible candidates for the dictionary form:
| Category | Hypothetical verb | Theory |
| Ichidan | およぎる | Oyogiru drops the ru to leave oyogi, then add masu |
| Godan | およぐ | Oyogu becomes oyogi, then add masu |
Both of these candidates are logically possible. They both, if they existed, would conjugate to a -masu form of oyogimasu.
So which one is it, oyogu or oyogiru? If you only know the -masu form, and you’re forced to guess, you should go with the changer. There are about twice as many of them as there are droppers.
However, if you also remember the -te form, you can deduce the dictionary form with certainty. You just take our little thought experiment above one step further. For each candidate, imagine what its -te form would be. Then compare it to the actual -te form and see which one produced the correct result. Let’s try that with oyogimasu:
| Category | Hypothetical verb | Hypothetical -te form | Actual -te form |
| Ichidan | およぎる | およぎて | およいで (no match) |
| Godan | およぐ | およいで (match!) | およいで |
Since we know the actual -te form is oyoide, then we know that oyogu is the correct dictionary form.
Now you try it. Let’s work backwards from kikimasu, “to hear.” There are two conceivable dictionary forms that could possibly produce a -masu form of kikimasu. Think about it, and then check your guesses.
| Category | Hypothetical verb | Hypothetical -te form | Actual -te form |
| Ichidan | ききる | ききて | きいて |
| Godan | きく | きいて (match!) | きいて |
Since we know that the actual -te form is kiite, we know that this must be the godan kiku.
Some are even easier. Take tabemasu, “to eat.” Since godan verbs conjugate to the -masu form by changing the last character to an i sound and then adding masu, there is no possible godan verb that could create tabemasu (the hypothetical tabu would become tabimasu, not tabemasu). So it has to be an ichidan, or dropper, and the dictionary form must be taberu.
Let's try a few more together. Let's do tachimasu, "to stand."
| Category | Hypothetical verb | Hypothetical -te form | Actual -te form |
| Ichidan | たちる | たちて | たって |
| Godan | たつ | たって (match!) | たって |
Walking through the logic, we think about what hypothetical verbs could produce tachimasu. We could have a dropper of tachiru or a changer of tatsu. Now, supposing that these hypothetical verbs really existed, we imagine what their -te forms would be. Finally, we compare to what we know is the real -em form, and we find that the dictionary form must be tatsu.
Let's try arimasu, "to exist."
| Category | Hypothetical verb | Hypothetical -te form | Actual -te form |
| Ichidan | ありる | ありて | あって |
| Godan | ある | あって (match!) | あって |
If you feel your brain swelling, don't worry—that's just the sensation of new neurons growing. This exercise is only a temporary crutch, but it's one that will really improve your ability to navigate Japanese verbs.
Let’s another together. We’ll do hanashimasu, “to speak.”
| Category | Hypothetical verb | Hypothetical -te form | Actual -te form |
| Ichidan | はなしる | はなして | はなして |
| Godan | はなす | はなして | はなして |
Uh oh. Both candidates produce the same -te form. Not to worry, though. This can be solved by one piece of knowledge: there are no ichidan verbs that end in shiru. None. So this must be a godan, hanasu.
This technique will help get you back to the dictionary form with 100% accuracy, as long as you remember the rule about no ichidan verbs ending with shiru.
One more and we'll call it a day. Let's try nomimasu, "to drink."
| Category | Hypothetical verb | Hypothetical -te form | Actual -te form |
| Ichidan | のみる | のみて | のんで |
| Godan | のむ | のんで (match) | のんで |
Now, believe me, I know that doing this feels like mental gymnastics, and it can be a little tiring. It’s good exercise, but you won’t have to do it for long. Once you have become familiar with the dictionary forms for the verbs you already know, you’ll just know in your gut that hanashimasu is really hanasu, and you’ll be able to skip this step. But for now, it is a reliable crutch and a good way to drill yourself on how conjugation works.
(Thanks for reading! Feel free to head back to the app to pick up where we left off.)