～ことができる: How to Say "Can Do" in Japanese

To say "can do" in Japanese with ～ことができる, attach this pattern to a verb's dictionary form. It states that an action is possible.¹ It is one of the two standard ways to express ability in Japanese. The other is the conjugated potential form.¹

Overview

What ことができる means and where it sits

～ことができる expresses ability or possibility: "can do" or "is able to do." It sits alongside the conjugated potential verb (可能動詞, kanōdōshi, "potential verb") as one of the two standard possibility expressions in Japanese.¹

The construction is the youngest of the Japanese possibility forms. 中野 (2008) catalogs their history and places verb-dictionary-form + ことができる as the last to emerge, in the late Edo period. It came after the older レル／ラレル forms and the fused potential verb.¹

The できる at its core is, historically, the potential form of する: 中野 (2008) states that "dekiru is originally the potential form of suru."¹ That single fact explains much of the pattern's behaviour, and it returns below.

A note on level before the mechanics.

N5/N4 here is a textbook convention, not an official ruling

The JLPT publishes no itemized grammar list. Its guide gives only can-do summaries by level.² This article places the affirmative recipe at N5 because 辞書形＋ことができます appears in Minna no Nihongo I, Lesson 18. It places the register contrast and negative at N4 because the conjugated potential verbs they rely on appear in Genki II, Lesson 13.³⁴

Register at a glance

Because the verb and できる are separated, the construction is analytic in shape. 中野 (2008) characterizes ～ことができる as 分析的 (analytic) and as 文章語として用いられる, "used as written or literary language."¹

This is the short preview of a fuller treatment below: ～ことができる leans formal and written, while the conjugated potential verb dominates everyday conversation. The full contrast lives under the nuance section.¹

The split is style-driven, not a hard grammatical rule. 中野 (2008) notes that the choice of possibility form depends on register, the verb involved, and the content of the sentence. The forms overlap rather than divide cleanly.¹

Form and construction

The recipe: Verb-dictionary form + ことができる

Attach ことができる to the plain non-past (dictionary) form of the verb. Nothing in front of こと conjugates. Only the できる at the tail carries tense and politeness.³⁵

Use the dictionary form for all three verb groups:

Verb group	Dictionary form	+ ことができる
五段 (Group I)	話す	話すことができる
一段 (Group II)	食べる	食べることができる
不規則 (Group III)	する / 来る	することができる / 来ることができる

Here is one worked example for each group. First, a 五段 verb.

写真しゃしんを撮とることができますか。⁶
"Can you take a picture?"

Then, a 一段 verb.

それを見みることができますか。⁶
"Can I see that?"

Then, an irregular する verb.

ここで勉強べんきょうすることができます。⁶
"You can study here."

Why the parts work: こと + が + できる

The pattern is built from three pieces, each with one job. こと nominalizes the verb phrase, turning the action into a thing: "the act of doing." が then marks that thing as the grammatical subject. できる asserts that the thing is possible.¹⁵

The diagram below shows the three-part decomposition for 泳ぐことができる.

This separation is what makes the construction analytic. 中野 (2008) contrasts it with the fused potential verb and the レル／ラレル forms because here the verb and できる stay apart rather than merging into one word.¹

The relevant sense of できる is the ability-or-possibility sense. 『デジタル大辞泉』 defines できる as "to have the ability or possibility to do that."⁷

The が marks the literal grammatical subject of できる: the nominalized act is "what is possible." That is why が, not を, is the correct particle before できる.³

Read it as "the act of -ing is possible"

Map こと to "the act," が to the subject marker, and できる to "is possible." This rebuilds the literal structure of 泳ぐことができる as "the act of swimming is possible." Holding that reading in mind makes it clear why が, not を, precedes できる.¹

Politeness: ことができる vs ことができます

Plain versus polite is shown entirely by the できる／できます at the tail. The dictionary-form verb plus こと in front never changes.³

Register	Non-past	Past
Plain	話すことができる	話すことができた
Polite	話すことができます	話すことができました

This is just できる behaving as an ordinary 一段 verb: できる → できます → できた → できました.⁷ The example below shows the plain past in context.

友人ゆうじんの機転きてんでなんとか助たすかることができた。¹
"Thanks to my friend's quick thinking, I somehow managed to be saved."

Noun + ができる (the boundary case)

When the action is already expressed by a noun, できる attaches directly to the noun through が, with no こと. This is common with する-verb nouns such as 運転 (driving) or 勉強 (studying). It also works with skill or language nouns such as 日本語 (Japanese) or テニス (tennis): ［Noun］＋が＋できる.⁷

This works because できる is the potential of する. The three shapes 運転ができる, 運転することができる, and 運転できる all point to "can drive."¹⁷

私わたしは、運転うんてんができます。⁶
"I can drive."

私わたしはテニスができます。⁶
"I can play tennis."

The only difference between 私は運転することができます and 私は運転ができます is whether 運転 is treated as a noun (＋が＋できる) or made back into a verb as 運転する and then nominalized (＋ことができる). The speaker's intended meaning is the same.⁶

The negative: ことができない

Forming ことができない / ことができません

Negate the pattern by conjugating できる at the tail. The dictionary-form verb in front does not change. できる becomes できない (plain) or できません (polite).⁷³

Register	Negative non-past	Negative past
Plain	話すことができない	話すことができなかった
Polite	話すことができません	話すことができませんでした

The こと construction does not add a special negative shape. できない is simply the regular 一段 negative of できる.⁷

が → は in the negative

In the negative, は frequently replaces が, giving ことはできない. は naturally carries contrastive scope, meaning it singles something out in contrast with other possibilities, and it pairs readily with negation. Hasegawa's analysis treats は as a focus particle whose contrastive reading is standard when it stands over a clause that is then negated.⁸

The effect is contrast. 書くことはできる implies "I can write, even if I can't do the other thing." ことはできない marks "this particular thing, at least, cannot be done," placing the negation on the nominalized act.⁸

The swap is optional and adds a shade of meaning. It is not obligatory. ことができない states neutral inability; ことはできない foregrounds contrast. Both are grammatical.⁸

Nuance and usage contexts

ことができる vs the conjugated potential form

The two forms share the same core meaning: "can" or "is able to." 中野 (2008) lists the conjugated potential verb and verb-dictionary-form + ことができる as members of one possibility-expression family. They are partly interchangeable.¹

The difference is register. ～ことができる is the analytic, written-leaning option, described by 中野 (2008) as 分析的 and 文章語. This contrasts with the fused character of the potential verb.¹ That is why the long form below can read as deliberate or stiff in casual speech, where the short potential verb 話せる is the conversational default.¹

日本語にほんごを話はなすことができます。⁶
"I can speak Japanese."

In conversation, 日本語が話せます would be the everyday equivalent of the sentence above.⁶

When ことができる is the better choice

Use ～ことができる in formal and written contexts, such as essays, announcements, rules, and business correspondence. Its analytic, deliberate tone fits its 文章語 character.¹

It is also a consistent fallback when a verb's conjugated potential form is awkward, ambiguous, or not standard. 中野 (2008) documents that potential-verb acceptability varies sharply from verb to verb, while the ～ことができる frame applies to any verb's dictionary form.¹

The long form is also clearer with long or complex verb phrases. The ability marker できる stays at the very end, and the verb phrase stays in its plain dictionary shape.¹⁵

Ability vs permission vs possibility

できる covers both ability and possibility. The sentence below shows the ability reading: the subject's own capacity to act.

何なにも言いいたくなければ言いわないことができる。¹
"If you don't want to say anything, you are able to not say it."

中野 (2008), drawing on 森田 (1995), frames the possibility senses as two relational types. One is situational possibility, where outside conditions allow the action. The other is ability possibility, where the subject has the skill. ～ことができる appears across both, leaning toward the general or situational reading rather than a purely inherent-skill one.¹⁹

Do not overload できる with a permission meaning

できる carries a secondary, context-dependent permission sense: 『デジタル大辞泉』 lists "is permitted to do so" among its suffix meanings.⁷ Treat ～ことができる as "is capable" or "is possible." When you mean "is allowed," use dedicated permission patterns such as ～てもいい, so the permission reading does not creep in where it is not intended.⁷

Good to know

Forcing ことができる onto an evaluative potential like 話せる

Some potential forms carry an idiomatic, evaluative meaning that the analytic ～ことができる does not. The phrase 話せる can mean "savvy" or "reasonable" rather than literally "able to speak," and ～ことができる cannot replace it. Writing あいつは話すことができる男だ for "he's a sharp guy" is awkward. 中野 (2008) marks that version with a question mark.¹ The natural sentence keeps the potential verb.

あいつは話はなせる男おとこだ。¹
"That guy is sharp." (here 話せる means "savvy," not "able to speak")

Fixed expressions and evaluative potentials stay with the conjugated potential verb. Proverbs and idioms show the same resistance. They tend to reject the analytic frame even in the negative.¹

Double-marking ability with the potential form plus ことができる

A common error is to conjugate the verb into its potential form and then add ～ことができる. This stacks two ability markers on one predicate. 食べられることができる is wrong because こと nominalizes a plain verb and できる already supplies "is possible" once. Pick one expression.³

食たべることができる。³
"Can eat."

The plain dictionary form is the required input, as every textbook recipe shows (辞書形＋ことができる). Alternatively, use 食べられる alone as the short potential form.³

こと is fixed here; の does not substitute

Elsewhere in Japanese, both こと and の can nominalize a verb, but this pattern is fixed with こと. の does not replace it inside ～ことができる. Treat this as a collocational fact, meaning a fact about which words naturally go together in this construction: the こと slot is frozen, the same way set phrases resist swapping in a synonym.¹⁵

できる began as the potential form of する

Knowing the etymology explains the whole pattern. 中野 (2008) states that "dekiru is originally the potential form of suru."¹ That is why 運転する pairs with both 運転できる and 運転することができる. It is also why ～ことができる behaves like "the act can be done," and why the same できる reappears in the noun ＋ ができる boundary case.¹

See also

• Japanese Verb Groups: 一段, 五段, and Irregular
• The Masu Form (ます): Polite Present and Future Tense
• Suru-Verbs (する-Verbs): How する Turns Nouns Into Verbs
• Polite vs. Plain Japanese: です/ます vs. だ (丁寧体・普通体)
• Japanese Complement Clauses with こと: The Abstract Nominalizer for Sentences-as-Nouns
• ～ことがある: How to Say "I Have Done X Before" in Japanese

References

Footnotes

1. 中野琴代「日本語の可能動詞」『下関市立大学論集』第52巻 第1・2合併号, 2008, pp. 1ff. https://ypir.lib.yamaguchi-u.ac.jp/sc/1683/files/140651 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷

2. 国際交流基金・日本国際教育支援協会「日本語能力試験 JLPT」公式案内（出題範囲について）. https://www.jlpt.jp/about/levelsummary.html ↩

3. スリーエーネットワーク編『みんなの日本語 初級I』第2版. スリーエーネットワーク, 2012. 第18課（辞書形＋ことができます）. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

4. 坂野永理ほか『初級日本語 げんき II』(GENKI: An Integrated Course in Elementary Japanese II) 第3版. The Japan Times, 2020. 第13課（可能動詞 / potential verbs）. https://wp.stolaf.edu/japanese/grammar-index/genki-i-ii-grammar-index/ ↩

5. Makino, Seiichi and Michio Tsutsui. A Dictionary of Basic Japanese Grammar. The Japan Times, 1986. Entry "koto ga dekiru." ↩ ↩² ↩³ ↩⁴

6. Tatoeba Project. Collaborative example-sentence corpus. https://tatoeba.org (sentence IDs cited inline; Japanese sentences with verified English translations). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

7. 『デジタル大辞泉』小学館. 「できる（出来る）」の項. https://www.weblio.jp/content/できる ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

8. Hasegawa, Akio. The Semantics and Pragmatics of Japanese Focus Particles. PhD dissertation, University at Buffalo (SUNY), Department of Linguistics. https://arts-sciences.buffalo.edu/content/dam/arts-sciences/linguistics/AlumniDissertations/Hasegawa%20dissertation.pdf ↩ ↩² ↩³

9. 森田良行『日本語の視点』(の発想を含む可能・受身・自発・尊敬の共通概念). 創拓社, 1995. (As cited and quoted in ¹, section 2.) ↩