The Japanese Potential Form: Saying What You Can Do

When a Japanese speaker reaches for the potential

The potential form appears whenever ability or possibility is the point of the sentence. Someone asks whether you can speak Japanese, whether you can come on Saturday, whether you can eat raw fish, whether the shop can deliver. In English these all use can plus a verb. In Japanese the verb itself changes shape, and the person you are talking to expects the answer to use the same shape back. If they ask hanasemasu ka, the natural reply is hanasemasu or hanasemasen, not a rephrased sentence.

It also carries meanings that English spreads across other words. Ikemasu can mean I am able to go, I am free to go, and going is possible for me, and the listener does not need to know which. That breadth is why the form is worth learning early. If you already know basic verb conjugation, the potential is the next change that lets you talk about yourself rather than only about what happens.

Building the potential form from any verb

For a godan verb the change is on the last syllable only. Ku becomes ke, su becomes se, mu becomes me, tsu becomes te, and u becomes e, then ru closes the word. Kaeru, to return, is a godan verb, so its potential is kaereru; a common learner error is to treat it as ichidan and produce kaerareru. Suru compounds follow suru, so benkyō suru becomes benkyō dekiru and unten suru becomes unten dekiru.

Every potential verb, whatever its origin, is an ichidan verb once formed. That means all further conjugation is easy: kakeru gives kakemasu, kakemasen, kakemashita, kakenai, and kakete, and taberareru behaves the same way. Two verbs resist the pattern. Wakaru already means to understand or be able to tell, so it has no potential in normal use, and aru has none either.

The ra-dropping form and where it belongs

In casual speech many Japanese speakers shorten the ichidan potential by dropping ra: taberareru becomes tabereru, mirareru becomes mireru, and korareru becomes koreru. This is called ra-nuki kotoba, ra-dropped language. It is widespread, especially among younger speakers, and it is useful, because the full taberareru is also the passive form and the short one can only be potential. The shape is still treated as nonstandard, though, and that affects where you can use it.

Use the ra-dropped form with friends, in casual chat and when you are matching the register of someone who uses it. Keep the full rareru form in polite conversation, at work, in writing of any kind, in a job interview and in every exam, where the short form is marked wrong. Godan verbs are not affected: nomeru and kakeru have no ra to drop. Learners who use the full form everywhere sound slightly formal but never incorrect, which is the safer error.

The particle shift from o to ga

When a verb takes the potential form, the thing you can do usually stops being a direct object and becomes the subject of an ability, so its particle shifts from o to ga. Nihongo o hanashimasu, I speak Japanese, becomes nihongo ga hanasemasu, I can speak Japanese. The same happens with dekiru, which never takes o: nihongo ga dekimasu, unten ga dekimasu. This is the form textbooks teach, and it is what you should say in polite conversation.

Real speech is more relaxed. Many speakers keep o, particularly when the object is long or when the sentence emphasises the action rather than the ability, and nobody will misunderstand you either way. Treat ga as the default and o as an option you may hear. Other particles do not change: ni, de and to stay exactly where they were, so tomodachi to hanasemasu and koko de kaemasu need no adjustment.

Potential form or koto ga dekiru

Koto ga dekiru attaches to the dictionary form and means the same thing: oyogu koto ga dekimasu and oyogemasu both say I can swim. The difference is register and weight. The potential form is shorter and is what people say in conversation. Koto ga dekiru sounds a little more formal and explanatory, which suits signs, announcements, written explanations, and sentences where the ability itself is being stressed. It also rescues you when you are not sure how to conjugate a verb.

A useful habit is to prefer the potential form when the verb is short and everyday, and to allow koto ga dekiru for long suru compounds or formal statements. Ryōgae suru koto ga dekimasu on a bank notice is normal; asking a friend whether they can swim with oyogu koto ga dekimasu ka sounds like reading from a manual. Both are correct Japanese, so the choice is about sounding natural, not about avoiding a mistake.

Verbs that already contain a can

A few verbs carry ability or possibility inside their basic meaning, and learners often build a potential form on top of them by mistake. Mieru means that something is visible, that it reaches your eyes without effort on your part: from this window the sea can be seen. Kikoeru does the same for sound. Mirareru and kikeru, the true potential forms of miru and kiku, mean that you are able to watch or listen because the opportunity, permission or equipment exists.

The contrast decides what you say when your video call fails. Koe ga kikoemasen means your voice is not coming through, a report about the sound, and is the sentence you want. Kikemasen would mean you are unable to listen, perhaps because you are busy. Wakaru sits in the same family: it already means to understand or to be able to tell, so wakarimasu is complete, and wakaremasu is a different verb meaning to split apart.

Saying you cannot

The negative is the polite masen or plain nai on the potential verb: taberaremasen, oyogemasen, dekimasen, koraremasen. Because every potential verb is ichidan, the plain negative simply swaps ru for nai, giving taberarenai and yomenai. Adding zenzen, not at all, or amari, not very much, before the verb sets the degree, and a mada at the front tells the listener that the ability is something you are working on rather than something you lack.

The last line is one of the most useful sentences in this post. Kikitoru, to catch what is said, is a godan verb, so its potential is kikitoreru, and the polite past negative kikitoremasen deshita tells a speaker exactly what went wrong without blaming them. A likely reply is mō ichido iimasu ne, followed by the sentence again more slowly.

Yō ni naru: talking about your progress

Learners rarely want to say that they can or cannot do something in the abstract. They want to say that they could not do it before and can now, and that is exactly what the potential form plus yō ni narimashita expresses. Kanji ga yomeru yō ni narimashita means I have become able to read kanji, and it carries the sense of a change that happened over time. Pair it with mae wa, before, and a negative to show the whole journey in one sentence.

Keep the potential inside this pattern when you mean ability. Yō ni naru with a plain dictionary form describes a change of habit instead: hashiru yō ni narimashita means I have started running, not that I have become able to run. For a goal you have not reached, use yō ni naritai desu: denwa de yoyaku ga dekiru yō ni naritai desu, I want to become able to book by phone. That sentence is a fine answer whenever a teacher asks what you are working on.

Declining without a flat cannot

A bare ikemasen or dekimasen is grammatically perfect and socially abrupt. It answers the question and closes the door. Japanese speakers usually soften a refusal with an apology, a reason introduced by the explanatory n desu, a trailing chotto that leaves the sentence unfinished, or a wish they could accept. The potential form is still in there, but it is wrapped, and the listener hears regret rather than rejection.

The most reliable frame is a positive wish followed by ga and a trailing reason: ikitai n desu ga, sono hi wa chotto. You never actually say you cannot, and the listener fills in the rest. When you must be explicit, lead with an apology and keep the reason short. Notice that these lines invite a reply such as sō desu ka, jā mata kondo, which lets both people move on without awkwardness.

A drill for the potential form

• Take ten godan verbs and say dictionary form, potential and polite potential in a loop: nomu, nomeru, nomemasu.
• Repeat with five ichidan verbs plus suru and kuru, saying the full rareru form every time.
• Ask yourself five ability questions with ga and answer each with a positive and a negative: sushi ga tsukuremasu ka, hai, tsukuremasu, iie, tsukuremasen.
• Describe three things you have become able to do since starting Japanese with yō ni narimashita, and one you want to reach with yō ni naritai desu.
• Turn down two imaginary invitations with n desu ga and a trailing chotto, then accept a third with ikemasu yo.