Koto ga dekiru (ことができる): how to say you can do something

Koto ga dekiru (ことができる) is a construction used to say that someone has the ability to do something or that an action is possible in a given situation. The basic structure is verb in dictionary form + ことができる.

In a sentence like 日本語を話すことができます, the action 日本語を話す (“speak Japanese”) is turned into a nominal unit by こと; then, できる states that this action is possible. In this guide, you will see how to form affirmative, negative, and past sentences, as well as the difference from the potential form.

What does koto ga dekiru mean?

The expression ことができる can be translated, depending on the context, as “can do,” “be able to do,” “be capable of doing,” or “be possible to do.” It combines three elements:

• こと: turns the preceding action into an abstract idea or “thing”;
• が: marks that nominalized action as what is possible;
• できる: indicates ability or possibility.

The Japan Foundation presents ことができる as a fixed expression in which こと cannot be freely replaced by の. If you have not yet mastered the form that appears before こと, review the simple form of Japanese verbs.

How to form sentences with ことができる

The main formula is:

[verb in dictionary form] + ことができる

The verb that describes the action remains in dictionary form. It is できる that takes the changes in formality, negation, and tense. See a basic example:

私は日本語を話すことができます。
Reading: わたしは にほんごを はなすことが できます。
Romaji: Watashi wa nihongo o hanasu koto ga dekimasu.
Translation: I can speak Japanese.

Within the action 日本語を話す, the particle を still marks the object of 話す. The が belongs to the ことができる construction. To review the role of these particles, see the guide on basic particles in japanese.

Personal ability and situational possibility

The construction serves two closely related meanings. The context indicates which one is highlighted.

Ability or skill

Use ことができる when someone knows how to or is able to perform an action.

マリアさんは漢字を読むことができます。
Reading: マリアさんは かんじを よむことが できます。
Romaji: Maria-san wa kanji o yomu koto ga dekimasu.
Translation: Maria can read kanji.

Possibility created by conditions

The same structure can indicate that an action is possible because of the place, the time, a rule, or another condition.

この図書館では無料で本を借りることができます。
Reading: この としょかんでは むりょうで ほんを かりることが できます。
Romaji: Kono toshokan de wa muryō de hon o kariru koto ga dekimasu.
Translation: In this library, it is possible to borrow books for free.

This distinction appears in the Irodori material from the Japan Foundation: できる can express both a personal ability and something possible in a given situation.

Affirmative, negative, and past forms

To change the tense or negate the sentence, conjugate できる. The verb before こと remains in the dictionary form.

The polite forms follow the same pattern studied in masu form of Japanese verbs.

negative present

今日は残業することができません。
Reading: きょうは ざんぎょうすることが できません。
Romaji: Kyō wa zangyō suru koto ga dekimasen.
Translation: Today I cannot work overtime.

Affirmative past

昨日、先生と話すことができました。
Reading: きのう、せんせいと はなすことが できました。
Romaji: Kinō, sensei to hanasu koto ga dekimashita.
Translation: Yesterday, I was able to talk to the teacher.

negative past

The train stopped, and I couldn't go to the company.
Reading: densha ga tomatte, kaisha e iku koto ga dekimasen deshita.
Romaji: Densha ga tomatte, kaisha e iku koto ga dekimasen deshita.
Translation: The train stopped, and I couldn't go to the company.

Koto ga dekiru and the potential form

ことができる and the potential form can convey ability or possibility, but they are different constructions.

Both sentences can mean “I can eat sashimi.” In many contexts, the potential form sounds more direct; ことができる can sound more explanatory or formal and is especially useful when the preceding action is long. To learn the conjugation rules for each verb group, see the guide on potential form of verbs in Japanese.

Do not mix the two constructions in the same expression. Use 食べることができる or 食べられる, and not a redundant combination like 食べられることができる.

How to use with nouns and する verbs

With some activities expressed by nouns, it is possible to directly use N + ができる.

My brother can cook.
Reading: ani wa ryōri ga dekimasu.
Romaji: Ani wa ryōri ga dekimasu.
Translation: My brother can cook.

With nouns linked to する, the form N + できる is also frequent and concise:

She can drive a car.
Reading: kanojo wa kuruma o unten dekimasu.
Romaji: Kanojo wa kuruma o unten dekimasu.
Translation: She knows how to drive a car.

運転することができます is also grammatical, but 運転できます is usually simpler. If verb formation still causes doubt, go back to the Verb groups in Japanese.

Three cautions with できる

1. Not every できる means “can”. In 駅の前にホテルができました, the meaning is “a hotel was built/opened in front of the station”.
2. Possibility and permission can be close. ここで写真を撮ることができますか can ask if it is possible or allowed to take photos; the context decides the reading.
3. Do not conjugate the first verb to mark tense. In “I managed to read”, use 読むことができました, keeping 読む in dictionary form.

Short dialogue with ことができる

A: この美術館では写真を撮ることができますか。
Reading: kono bijutsukan de wa shashin o toru koto ga dekimasu ka?
Romaji: Kono bijutsukan de wa shashin o toru koto ga dekimasu ka?
Translation: In this museum, is it possible to take photos?

B: 一階では撮ることができますが、二階ではできません。
Reading: ikkai de wa toru koto ga dekimasu ga, nikai de wa dekimasen.
Romaji: Ikkai de wa toru koto ga dekimasu ga, nikai de wa dekimasen.
Translation: On the first floor you can, but on the second you can't.

In the second statement, the complete action can be omitted after it has already been mentioned. This economy is common when the context makes clear what できません refers back to.

Quick summary

• Use verb in dictionary form + ことができる for ability or possibility.
• Conjugate できる, not the verb that comes before こと.
• Use できない/できません for negation and できた/できました for the past.
• The potential form conveys a similar idea, but it is shorter.
• With activities in する, forms like 運転できる are common.

Next Steps

Practice transforming simple actions, such as 読む, 書く, 行く, and 勉強する, into sentences with ことができる. Then, write the same idea with the potential form and compare the structure of the two versions. To organize longer sentences without relying on a rigid order in Portuguese, also refer to the method for form sentences in Japanese.

Sources and review

• Japan Foundation: uses and nominalization of こと
• Irodori — Lesson 5: V-ることができます
• Irodori: comparison between ことができる and the potential form