How does potential form + ように differ from できるように


How does the structure (potential form + ように) meaning "in order to do
something in the future" differ from できるように "have the ability to do something
in the future"?

For example:

> たくさんことばが **覚えられるように** 、日本語の本を読んでいます。  
>  In order to learn a lot of words, I am reading books in Japanese.

How does this differ from:

> たくさんことばが **覚えることができるように** 、日本語の本を読んでいます。




ことば **が/を** 覚えられるように and ことば **を** 覚えることができるように have no "meaning" difference.
You are literally saying the same thing. But it is far more natural to use the
potential form + ように to describe wanting to be able to do something _as a
reason for_ why you are doing some other thing.

「友達と一緒に遊べるように泳ぐ練習をしています」 is more fluid and natural sounding than
「。。。遊ぶことができるように」 in that sentence. Think of it like the difference between
saying: "so that I will be able to play" vs the more natural: "so I can play".

「ができる」, on the other hand, is most often used on its own, to make a special
point of explaining something that you can do. For example, a sentence like
「私はピアノを弾くことができる」 is a simple declaration of ability. This is by far the most
common usage of the 「ができる」 pattern.

I have heard 「V+ことができるように。。。」 before, but it's rare, and as far as I can tell
it's used mostly to strongly emphasize striving for the _ability_ to do
something, where that ability is the main goal... the difference between
"studying Japanese so I can understand it" and "studying Japanese so I'll be
able to understand my wife's parents".

