Potential II: できる
Other than using られる with 一段 verbs and changing 五段 into special potential verbs, you can also use できる in the pattern ～ことができる. できる more or less correlates to the potential form of する. As you can see, though, they do not come from the same word.
できる
する’s potential form is できる・出来る. You don’t have to add or do anything else. In Japanese, you can use できる with things regarding ability. So, the equivalent of “can English” would be a valid expression.
1. 努力と運が相まって優勝できた。
Together with effort and luck, I was able to be victorious.
2. 加藤さんは碁が出来ます。
Mr. Kato can play go.
3a. 日本語ができます。〇
3b. 日本語を話しができます。X
I can speak Japanese.
Literally: I can do Japanese.
Grammar Note: You don’t make a verb a noun and use “Noun + ができる (see ことができる). This example shows how できる can show ability/talent. So, ゴルフができない would also be correct.
4. 彼らは賛成も反対もできない。
They can’t even agree or disagree.
5. もう一泊できますか。
Can I stay for one more day?
Meanings Other Than Potential
The 可能形 is unable to show appearance or what something is made of, but できる sure can. Those are the “other” usages of it mentioned at the beginning of this lesson.
6. 水は酸素と水素からできている。
Water is made up of oxygen and hydrogen.
7. ご飯、できましたよ。
Dinner is made!
8. 人生って、悩みと苦しみからできてるんだなあ。 （男性語）
Life really is made from worries and suffering.
9. 人間は体と心からできているのに、みんな体のことばかりに一生懸命気を使って、心のほうに栄養を与えることを忘れている。
Although humans are made up of the body and the heart, everyone focuses solely on their bodies and forget about providing nurture to their hearts.
～ことができる
Instead of using ～（ら）れる, you may use ことができる. This pattern is arguably more common despite being longer. Without qualification, it will sound as if you can’t do the phrase at all when used in the negative. This does not have the requirement of being only used with verbs of volition. This can be used to show the potential of something to happen.
10. 私は日本語を話すことができます。
I can speak Japanese.
11. コンピューターを使うことができるか。 （Rough)
Can you use a computer?
12. アメフトの試合を見ることができました。
I was able to see the American football game.
13. １００万からの署名を集めることができないでしょう。
You won’t be able to collect over a million signatures.
14. その漢字を読むことができませんでした。
I could not read that Kanji.
Particle Note: が in this pattern, due to its specific nature, would otherwise make it sound like you in particular are the one that “can”; however, this is not necessarily the case. Nowadays, ～ことができる has more or less become an affirmative, refined pattern.
～することができる
～することができる shouldn’t be used excessively, and it should be avoided in promotion-oriented settings. However, it shows up a lot in magazines and such because it is felt by many to be more polite. Yet, when there is a word limit, できる should do. For a minority of speakers, this phrase is ungrammatical. However, this is an extreme position based mainly on a misconception of case marking in Japanese. In the potential, が does not mark a subject. It marks an object. This may be confusing, but other languages have similar alignment rules. This is simply a quirk in Japanese, and it’s not like natives were confused on how to deal with it until being introduced with half-baked knowledge about Western grammar terms.
15. ダウンロードすることができます！
You can download it!
Other Ways to Make する Potential
There are four potential routes that you can take to make the potential with する-verbs.
- Single characters like 愛 that become verbs with する
→+ することができる; -し得（え・う）る; + せる. - Compounds/loan words–経験–that become verbs with する.
→+ （することが）できる; し得る. - Verbs with する that become voiced such as 感ずる・じる.
→Conjugate as 一段 verbs; -じ得る; + ことができる. - Verbs with a っ such as 発する.
→+ ことができる; -得る.
Verb Note: Verbs like 愛す are treated as 五段 verbs. Also note that something like 理解することができる is typically deemed to be unnecessarily wordy.
Curriculum Note: See Potential III for ～得る.
16. 彼は危険を察することができないやつだな。
He’s a guy that can’t sense danger, isn’t he?
17. 君を愛せない。
I can’t love you.
18. 経験（《すること》が）できる。
To be able to experience.
19. 彼は誰でも愛せる人だね。
He’s a person that can love anybody, isn’t he?
20. これでも中学生の時に日本語を理解できませんでした。
Believe it or not, I couldn’t understand Japanese in junior high.