Capability: the potential one has to harness a particular skill
First, let me say, great question!
Whilst the two words are often used interchangeably, there is a subtle difference between the two.
Ability refers to how much one can do in the current moment, how much one has developed a skill so far.
Whereas, capability refers to how much potential one has to develop a skill, what they could achieve if they continued to work at it.
When you are the best you can possibly be at something, your ability and capability will be the same.
Example sentences:
"The gold medalist proved their running ability was the best in the world right now. However, experts believe the silver medalist has the capability to win in the next event."
"The teacher was concerned about the student's writing and reading ability, though she continued to believe that he had the capability to improve."
まず、とてもいい質問ですね！
これら2つの言葉は、同じように使うこともできますが、やや違いがあります。
Abilityは、今の段階でどれくらいできるか、どれくらいスキルを得たかを表します。一方、 capabilityは、スキルを得るのにどれくらいの可能性があるか。それをし続けたら成し遂げることができるであろうということを表します。
あることに対して得意なときには、your abilityとcapabilityは同じ意味になります。
例文：
"The gold medalist proved their running ability was the best in the world right now. However, experts believe the silver medalist has the capability to win in the next event."
（金メダリストが今世界で最も優れたランニング能力を証明した。しかし、専門家は、銀メダリストは次の大会で勝つ可能性があると信じている。）
"The teacher was concerned about the student's writing and reading ability, though she continued to believe that he had the capability to improve."
（その生徒はライティングとリーディング力が上達すると思い続けていたが、先生は心配していた。）
He has the ability to achieve the pass rate he will need for university.
Achieving the pass rate for university is well within his capabilities.
He has the ability to do the job well, and the capabilities to progress in the company.
The first phrase refers to the fact that the person is already equipped with the skills to achieve their goal, such as gaining a place at university.
The second phrase focuses more on the potential of the person to achieve their target, and infers that, provided they apply themselves to the task in hand, they are capable of achieving this.
The third phrase contrasts the slight difference in the two words. The first part of the sentence states the persons ability as a fact, and the second part refers more to their future potential.
Capability : the potential a person has to do something or have a certain skill.
We would use the word, "ability," to talk about a skill that someone has/hasn't to do or complete a task.
Example sentence : He has the abilities needed to be a great craftsman.
We would use the word, "capability," to talk about a conditional idea that someone has the ability to do something if they wanted to. This word caters more to the possibility or something and isn't certain yet.
Example : He has the capability to be a great craftsman if he tried harder.
"ability"は、あるタスクを達成するスキルのことを話すときに使います。
例文：
He has the abilities needed to be a great craftsman.
（素晴らしい職人になるために必要な能力を持っている。）
"capability"は、人がもししたいときに何かをすることができる条件付きの能力のことです。可能性やまだ確かではないことについて話すときに使います。
例文：
He has the capability to be a great craftsman if he tried harder.
（彼は、もしもっと頑張ったら素晴らしい職人になることのできる可能性がある。）
He is not capable of stealing money because he is a very honest person.
He is able to be at work on time because he leaves home very early.
The best time to use the word capable, is it to use it to describe personality or nature of a person or thing.
Being able to do something means that it can be done, it is possible.
They are interchangeable, but these are the safest ways to use these two synonyms.
capableは、個人的なこと、その人やもののもった能力のことを指します。
Being able to do something とは、あることができる、可能であるという意味です。
これらは同じように使うことができますが、これらがこの類義語を使う最も安全な方法と言えるでしょう。
Ability: is the capacity to be able to do something
Capability: is possessing the potential to be able to do something.
The words "ability" and "capability" have similar meanings with very little difference. The key difference when you speak of someone's capabilities is that it implies the potential to be able to do something rather than just actual ability.
You may use these terms in a sentence in the following ways:
-The job requires the ability to travel when needed. It's important that the candidate should not have family ties or children.
-The candidate for the job should be capable of working in a team, meet deadlines and pay attention to detail.
"ability" と "capability" は意味が近いですが、重要な違いとして、"capability" には「潜在能力」のニュアンスがあります。
これらの語は文の中では次のように使うことができます。
-The job requires the ability to travel when needed. It's important that the candidate should not have family ties or children.
（この仕事では適宜出張が必要になります。子どものある人や家族との絆の深い人には難しい）
-The candidate for the job should be capable of working in a team, meet deadlines and pay attention to detail.
（この仕事には「協調性」や「締切が守れる」「細部に目が行き届く」などの能力が求められる）
Ability: Is having the means to do something, not necessarily referring to skill.
Capability: is being capable of achieving a certain end, skill related.
I have the ability to approve this client's loan.
He has the capability of winning gold in next year's Olympic.
I have the ability to approve this client's loan.
（このクライアントのローンを承認する力があります。）
He has the capability of winning gold in next year's Olympic.
（彼は、来年のオリンピックで金メダルを勝ち取る力がある。）
Ability means you have the skills or means to do something
Capability is the measure of your ability or the feature of being capable of something
When you know someone can do something, you know their ABILITY.
She has the ability to win the entire competition!
When you know how someone can do something, you know their CAPABILITIES(capability).
She is the only one in the game that can actually play.
ある人に何かがができることを知っているなら、それはその人の "ABILITY" を知っているということです。
例：
She has the ability to win the entire competition!（彼女には総合優勝する力がある）
ある人があることをどのようにできるか知っているなら、それはその人の "CAPABILITIES" を知っているということです。
例：
She is the only one in the game that can actually play.（その試合で実際のプレーできるのは彼女だけ）
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