Use the short potential form (話せる, with が) in everyday speech, and switch to 〜ことができる (with を, unchanged) when the situation calls for something more formal or written.
This guide is for N5-N4 learners who already know basic verb forms. After reading, you’ll build 話せる, 食べられる, and できる correctly, and know which “can” pattern fits a text message versus a formal email.
Quick summary: Japanese has two “can” patterns — conjugate the verb itself for casual speech, or add ことができる for formal speech, and the object marker changes depending on which one you pick.
| Feature | Short Potential (話せる) | ことができる (話すことができる) |
|---|---|---|
| Formation | Conjugate the verb: godan u→e+る, ichidan る→られる, irregular する→できる, 来る→来られる | Dictionary form + ことができる, no conjugation change |
| Object marker | が (日本語が話せます) | を stays (日本語を話すことができます) |
| Register | Casual, everyday spoken Japanese | Formal, written, polite requests, announcements |
| Typical scenes | Texting friends, quick questions to staff | Signs, emails, interviews, customer service scripts |
- Why 話せる Isn’t Just 話す + ‘Can’
- The One-Question Test: 話せる or 話すことができる?
- How to Build 可能形: From 話す to 話せる, 食べる to 食べられる, する to できる
- 話せる Wants が, 話すことができる Keeps を
- 食べられる Can Mean ‘Can Eat’ or ‘Gets Eaten’ — Here’s How to Tell
- FAQ: Japanese Potential Form Questions
- Quick Quiz: Test Your Potential Form Skills
- Summary: Choosing Between 話せる and ことができる
Why 話せる Isn’t Just 話す + ‘Can’
English Bolts ‘Can’ On; Japanese Rebuilds the Verb
In English, “can” is a small helper word. You drop it in front of almost any verb: can speak, can eat, can go.
Japanese doesn’t work that way. There is no separate word for “can” that sits next to the verb.
Instead, the verb itself changes shape. 話す becomes 話せる. The new word carries “can” built inside it.
Think of the difference between “I can swim” and “I am able to swim” — same meaning, but “able to” sounds more formal, like something from a report or announcement.
In English, swapping “can” for “is able to” is just a style choice. Nothing else in the sentence has to change.
In Japanese, the choice comes with real grammar. The short potential form re-marks its object with が, while ことができる leaves the original を untouched.
Because English never changes its object word when adding “can,” learners often keep を even after switching to the potential form. That’s the exact spot where が is expected instead.
The One-Question Test: 話せる or 話すことができる?
Casual Voice vs Formal Voice, Not Right vs Wrong
Am I chatting or speaking casually, or writing/saying something formal (a sign, an email, a polite ask to a stranger)? Casual → conjugate the verb into potential form and mark the object with が. Formal → keep the dictionary-form verb and add ことができる, object stays を.
Say you’re texting a friend about Wi-Fi at a cafe. That’s casual, so you’d say 使える, not 使うことができる.
Now imagine the same fact printed on a sign at the cafe entrance. A sign is formal and written, so 使うことができます fits better there.
How to Build 可能形: From 話す to 話せる, 食べる to 食べられる, する to できる
Three Verb Groups, Three Small Changes
Godan verbs shift their last sound from the u-row to the e-row, then add る. 話す becomes 話せる, and 入る becomes 入れる.
Ichidan verbs are simpler. Drop the final る and add られる, so 食べる becomes 食べられる.
The two irregular verbs just have to be memorized. する becomes できる, and 来る becomes 来られる.
Japanese: この会員証があれば、深夜でも入れますよ。
Romaji: Kono kaiinshou ga areba, shinya demo hairemasu yo.
English: If you have this membership card, you can get in even late at night.
Why: 入る (godan) becomes 入れる by shifting the final sound to the e-row and adding る — the everyday way staff explain access casually.
Japanese: 今日、予約なしでも切れますか?
Romaji: Kyou, yoyaku nashi demo kiremasu ka?
English: Can you cut my hair today even without an appointment?
Why: 切る is a godan verb, so its potential form shifts the final sound to the e-row and adds る (切る→切れる) — the same pattern as 話す→話せる.
話せる Wants が, 話すことができる Keeps を
Why the Object Marker Changes When the Verb Does
Once a verb turns into its potential form, it stops acting like a plain action word. It now describes what’s possible, and that shift moves the focus onto the thing being made possible.
That’s why が steps in. 日本語が話せます puts the spotlight on “Japanese” as the thing within reach, not just an object being acted on.
ことができる works differently. It treats “can” as an extra phrase tacked onto a normal verb phrase, so the original を never has a reason to move.
Japanese: 辛さ、変えられますか?
Romaji: Karasa, kaeraremasu ka?
English: Can I change the spice level?
Why: The short potential form (変える→変えられる) is quick and conversational — the natural register for asking a question at the counter.
Japanese: 麺の量を増やすことはできますか?
Romaji: Men no ryou o fuyasu koto wa dekimasu ka?
English: Would it be possible to increase the amount of noodles?
Why: ことができる keeps the dictionary form and the original を, and reads as more formal/careful — useful with a more reserved staff member or through a form.
食べられる Can Mean ‘Can Eat’ or ‘Gets Eaten’ — Here’s How to Tell
And Why 話せた Sometimes Means ‘Managed To,’ Not Just ‘Could’
For ichidan verbs, the potential form and the passive form look exactly the same. 食べられる can mean “can eat” or “gets eaten,” depending on context.
Past-tense potential adds another layer. できた or 取れた often means “managed to” that one time, rather than describing a general skill.
Unnatural: 日本語を話せます。
Natural: 日本語が話せます。
English keeps the object of “can” unchanged — “I can speak Japanese” still has “Japanese” as the object. Learners assume the Japanese object marker never moves either, but potential verbs re-mark their object with が.
Common Mistake: 漢字が読めることができます。 This stacks two “can” systems at once. Say either 漢字が読めます or 漢字を読むことができます, never both together.
Japanese: このケーキ、まだ食べられますか?
Romaji: Kono keeki, mada taberaremasu ka?
English: Can this cake still be eaten? / Is this cake still uneaten?
Why: 食べる is ichidan, so its potential and passive forms are identical (食べられる) — only context tells you whether you’re asking about edibility or about whether someone has eaten it.
Japanese: 今日、予約取れてよかった!
Romaji: Kyou, yoyaku torete yokatta!
English: I’m so glad I managed to get an appointment today!
Why: 取れて (potential of 取る) here means “managed to/succeeded that one time,” not a general standing ability.
FAQ: Japanese Potential Form Questions
What’s the difference between 食べられる as potential and as passive?
They’re identical in form for ichidan verbs. 食べられる means “can eat” when it’s about your own ability (“I can eat spicy food”), and “gets eaten” when it’s passive (“the cake got eaten”). Context and the rest of the sentence usually make it clear which one is meant.
Do I use が or を with the potential form?
With the short potential form (話せる, 読める, etc.), the thing you can do is usually marked with が, not を — 日本語が話せます, not 日本語を話せます. If you use ことができる instead, the original を stays: 日本語を話すことができます。
Is 〜ことができる more polite than the short potential form?
It’s more about formality and register than politeness level. ことができる sounds more formal and written, the kind of phrasing in a manual or job interview, while the short potential form (話せる) is what native speakers use in everyday conversation, even at a polite level.
Quick Quiz: Test Your Potential Form Skills
Try these three questions before checking the answers below.
- Conjugate 読む into its potential form (polite, present).
- What are the two possible meanings of “このケーキ、明日まで食べられるかな?”
- Which is more natural in a casual text to a friend: “ここでWi-Fiが使えるよ” or “ここでWi-Fiを使うことができます”?
1. 読めます (yomemasu) – 読む is a godan verb — shift the final u-sound (む) to its e-sound counterpart (め), add る, then make it polite: 読める→読めます。
2. Either “I wonder if this cake can still be eaten by tomorrow (still edible/possible)” or “I wonder if this cake will get eaten by tomorrow (someone will finish it).” – 食べられる is identical in shape for potential and passive with ichidan verbs. Without more context, the sentence could ask about the cake’s edibility (potential) or about whether someone will finish it (passive) — tone and surrounding talk decide which is meant.
3. ここでWi-Fiが使えるよ – Short potential form with が fits casual speech to a friend, while ことができる with を sounds too formal for a quick text.
Summary: Choosing Between 話せる and ことができる
- Short potential form (話せる) conjugates the verb itself and marks the object with が.
- ことができる keeps the dictionary form and the original を, and sounds more formal.
- Godan, ichidan, and irregular verbs each build their potential form in a different small way.
- Ichidan potential and passive forms look identical, so context decides the meaning.
- Past-tense potential often means “managed to” rather than a general standing ability.
Once these two “can” patterns feel natural, the next useful step is looking at other verb forms that shift meaning with context, like the passive and causative forms.
