This is often used for actors who can learn a part very quickly, or musicians who can learn a new song very quickly.
-- He had no trouble filling in for the star, because he's a quick study.
-- The band had to find a new lead guitarist at the last minute. Fortunately, she's a quick study, so the concert went well.
But it also can be used for academic achievements
-- She arrived at school two weeks later, but she's a quick study, so she had no trouble catching up.
これは自分のパートを覚えるのが速い役者や、新しい歌を覚えるのが速いミュージシャンに良く使われる言葉です。
例文：
-- He had no trouble filling in for the star, because he's a quick study.
（彼は主役を張るのに全く問題ないよ。なにしろ、物分かりがいいからね。）
-- The band had to find a new lead guitarist at the last minute. Fortunately, she's a quick study, so the concert went well.
（バンドのリードギタリストを直前になって新たに見つけなければいけませんでした。幸いにも、習得が速い人だったので、コンサートはうまくいきました。）
一方で、学業成績を表すためにも使える表現です。
-- She arrived at school two weeks later, but she's a quick study, so she had no trouble catching up.
（彼女は2週間遅れて学校に入ったけど、物分かりが良いので、何の問題もなく遅れを取り戻すことができました。）
If you get something it means that you understand it.
"I dont get why Jill likes Tom more than Henry."
To catch on to something means to comprehend a situation or to learn to do something.
"Peter caught on to playing chess very quickly snd is now very hard to beat."
To get xxとはxx理解しているという意味です。
"I dont get why Jill likes Tom more than Henry."
「なぜJillがHenryよりもTomが好きなのか理解できない」
To catch on to xx はxxを理解している、もしくはxxすることを学んでいるという意味です。
"Peter caught on to playing chess very quickly snd is now very hard to beat."
「Peterはチェスの仕方をとても早いスピードで理解し、今では彼を打ち負かすことがとても難しいです」
*Fast learner -is a person who quickly learns or catches things fast.
Example Sentences:
Joe is a fast learner, he got his driver's licence easily.
I instructed him just once and he executed the task perfectly.
Fast learner は、物事をすぐに学習し、理解する人です。
例文
Joe is a fast learner, he got his driver's licence easily.
ジョーは物覚えが凄く良いんだ、免許証も簡単に取ったよ
I instructed him just once and he executed the task perfectly.
彼にはたった1回教えただけだけど、仕事を完璧にやったよ。
We can use the adjectives, quick or fast, to talk about how easily or quickly it is for someone to learn something. We can also say that, "someone catches on fast," to describe that they are able to understand concepts very quickly and easily.
南アフリカ 
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