ことができる versus V~える form

Question

Way back in the day when I was first learning Japanese, I learned that you could add ことができる to a verb to indicate potential. Like so:

食{た}べることができる

(I) can eat (something)

It became my habitual way of expressing possibilities.

Then later, I learned that you could just modify the verb and get the same thing:

食{た}べられる

(I) can eat (something)

I know that this is also the passive voice, but, unless I'm mistaken, it can be used strictly as a way of expressing potential.

I still tend to habitually say ことができる, though. It tends to jump out of my mouth before I realize that I could have probably modified the verb. I think because my brain thinks they are the same thing, so I just go with the usual.

So... are they different?

Answer 1

Very simply :

• 食べることができる

  I am technically able to eat. I have a mouth, a stomach, and so on. When you ask "can you do this for me" and your witty friend replies "yes, I can" but doesn't do it, that's this meaning of potentiality that he chose to understand. You'd use this form to say "I cannot time travel" or "I cannot fly". You cannot do anything about it, you're not responsible (which is a very Japanese way to say things).

• 食べられる

  I can eat, in the other meanings :)

  For example, "I can't go with you because I have some work to finish". Technically, you can go, but for some reason, you must abstain from going. You can do something about it, you're responsible for not going/doing.

Answer 2

I'm a native speaker. The expressions of ことができる and ～られる are almost the same meaning. Don't think so difficult. You can use the expression you prefer.

Examples:

雨が止んだら、テニスに行くことができるよ！
雨が止んだら、テニスに行けるよ！

They have the same meaning. Both of them are used in daily life conversations. There is not the difference between the two sentences in my linguistic sense.
ことができる does not depend on in particular saying about the technical potential or saying something in the context about uncontrollable things.

こつこつ日本語勉強するなら、難しい漢字も読めるようになるよ。
こつこつ日本語勉強するなら、難しい漢字も読むことができるようになるよ。

The same meaning !!

これが終われば、寝られるよ。
これが終われば、寝ることができるよ。
You finish this, then you may go to bed.

Those sentences are also in the same meaning.
And furthermore, in the linguistic sense, ことができる and られる don't have any differences whether being polite or impolite. Both of them are used in conversations of family, friends, lover, business situations, polite situations, and so on.

When I want to emphasize the potential or capability in the context, I tend to use ことができる. But they basically have the same meaning.

Answer 3

I think ～ことができる has more to do with the potentiality (real word?) of things out of your control and ～（ら）れる has more to do with your abilities or things you can control.

• 雨が止んだら、テニスにいくことができるよ！　→　After the rain stops, we'll be able to go play tennis (can't control the rain).
• こつこつ日本語勉強するなら、難しい漢字も読めるようになる。　→　If you keep up with your Japanese studies, you'll be able to read even difficult kanji. (can control this)

Of course, this is a slight nuance, and I think the two forms overlap a great amount.

Answer 4

I'm not entirely sure, but ことができる I think is more 固い表現 than using the potential verb. And is usually taught before the potential form because grammatically structures are easier for students to pick up.

here is a forum with the same exact question btw

http://forum.wordreference.com/showthread.php?t=135581