Expressions of Ability and Potential Verbs in Japanese

The concepts of ability and potential are expressed in two separate ways

In written and spoken Japanese, the concepts of ability and potential can be expressed in two different ways. It will depend upon whom you're speaking with to determine which verb form you're going to use. 

The potential form of a verb can be used to communicate the ability to do something. It may also be used to ask for something, as English speakers often do with a similar construct.

For example, the speaker of question "can you buy the tickets?" probably doesn't doubt that the person he is speaking to is physically able to buy the tickets.

It's intended to ask whether the person has enough money, or whether the person will take care of this task on the speaker's behalf. 

In Japanese, attaching the phrase koto ga dekiru (~ことができる) after the basic form of the verb is one way to express ability or qualification to do something. Literally translated, koto (こと) means "thing," and "dekiru (できる)" means "can do."  So adding this phrase is like saying "I can do this thing," referring back to the main verb. 

The formal form of koto ga dekiru (~ことができる) is koto ga dekimasu(~ことができます), and its past tense is koto ga dekita (~ koto ga dekimashita).

Here are some examples:

Nihongo o hanasu koto ga dekiru.
日本語を話すことができる。
I can speak Japanese.
Piano o hiku koto ga dekimasu.
ピアノを弾くことができます。
I can play piano.
Yuube yoku neru koto ga dekita.
夕べよく寝ることができた。
I could sleep well last night.

 dekiru (~できる) can be directly attached to a noun, if a verb is closely associated with its direct object.

For instance:

Nihongo ga dekiru.
日本語ができる。
I can speak Japanese.
Piano ga dekimasu.
ピアノができます。
I can play piano.

 

Then there's what's known as a verb's "potential" form. Here are some examples of how to form a potential version of a Japanese verb:

 Basic formPotential form
U-verbs:
replace the final "~u" 
with "~eru".
iku (to go)
行く
ikeru
行ける
kaku (to write)
書く
kakeru
書ける
RU-verbs:
replace the final "~ ru" 
with "~ rareru".
miru (to see)
見る
mirareru
見られる
taberu (to eat)
食べる
taberareru
食べられる
Irregular verbskuru (to come)
来る
koreru
来れる
suru (to do)
する
dekiru
できる

 

In informal conversation, ra (~ら)is often dropped from the potential form of verbs ending in -ru. For example, mireru (見れる)and tabereru (食べれる)would be used instead of mirareru (見られる) and taberareru (食べられる).

The potential form of the verb can be replaced with the form using  koto ga dekiru (~ことができる. It is more colloquial and less formal to use the potential form of the verb.

Supeingo o hanasu 
koto ga dekiru.

スペイン語を話すことができる。
I can speak Spanish.
Supeingo o hanaseru.
スペイン語を話せる。
Sashimi o taberu koto ga dekiru.
刺身を食べることができる。
I can eat raw fish.
Sashimi o taberareru.
刺身を食べられる。

 

Examples of Translating Ability or Potential  into Japanese Verb Forms

 

 I can write hiragana.Hiragana o kaku koto ga dekiru/dekimasu.
ひらがなを書くことができる/できます。
Hiragana ga kakeru/kakemasu.
ひらがなが書ける/書けます。
 I can't drive a car.Unten suru koto ga dekinai/dekimasen.
運転することができない/できません。
Unten ga dekinai/dekimasn.
運転ができない/できません。
Can you play guitar?Gitaa o hiku koto ga dekimasu ka.
ギターを弾くことができますか。
Gitaa ga hikemasu ka.
ギターが弾けますか。
Gitaa hikeru. 
ギター弾ける?
(With rising intonation, very informal)
Tom could read this book 
when he was five.
Tomu wa gosai no toki kono hon o yomu koto ga dekita/dekimashita. 
トムは五歳のときこの本を読むことができた/できました。
Tomu wa gosai de kono hon o yometa/yomemashita.
トムは五歳でこの本を読めた/読めました。
Can I buy the ticket here?Kokode kippu o kau koto ga dekimasu ka.
ここで切符を買うことができますか。
Kokode kippu o kaemasu ka. 
ここで切符を買えますか。
Kokode kippu kaeru.
ここで切符買える? 
(With rising intonation, very informal)