What is an English adjective that means "able to learn new things quickly"? [closed]

What is an English adjective to describe the following skill: "able to learn new things quickly"?

For example:

Billy is very _________, as he learns new skills more quickly than an average person.

Fast learner or quick learner

I would say clever, quick-witted or, informally, smart:

clever (adjective)
quick to understand, learn, and devise or apply ideas; intelligent.

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quick-witted (adjective)
showing or characterized by an ability to think or respond quickly or effectively.

here are some words that came to mind - sagacious,

Exhibiting or marked by keen intellectual discernment, especially of human motives and actions; having or proceeding from penetration into practical affairs in general; having keen practical sense; acute in discernment or penetration; discerning and judicious; shrewd: as, a sagacious mind.

there's astute,

Quick at seeing how to gain advantage, especially for oneself; shrewd; critically discerning.

and of course, polymathic

Pertaining to polymathy; acquainted with many branches of learning.

and autodidactic :)

Relating to or having the characteristics of an autodidact; self-taught.

Sponge - a person or thing that absorbs something freely: His mind is a sponge gathering historical data.

I have often heard sharp used in this context.

mentally acute; clever; astute

Synonym discussion:

intelligent, quick have varying implications. Sharp suggests an acute, sensitive, alert, penetrating quality: a sharp mind. Keen implies observant, incisive, and vigorous: a keen intellect. Intelligent means not only acute, alert, and active, but also able to reason and understand: an intelligent reader. Quick suggests lively and rapid comprehension, prompt response to instruction, and the like: quick at figures.