Question: In general in English, we don't ever apply the definitive article to languages. We don't say "He speaks the Japanese" or "It was originally written in the French."

But for translated books, they are very often prefaced with a note phrased as *Translated from the Spanish* or *Translated from the Arabic*.

Where does this odd form originate? What is the reason for this grammatical deviation?

Answer: 
“the *adj*” is a reduced form that removes a noun (which is usually obvious from context) because the adjective is what really matters.

In this case, “the Spanish” probably means “the Spanish version”, though there are several other words that would give the same overall meaning.
In English, the definite article "*the*" has often been used in an idiomatic way with the names of things that wouldn’t appear to need an article..

Once, the use of "*the*" with a language was much more prevalent than it is today. Here are two old citations from the Oxford English Dictionary:

> 
> *"[Let not your studying the French make you neglect the English](https://books.google.ch/books?hl=fr&id=E24EAAAAYAAJ&q=%22Let+not+your+studying+the+French+make+you+neglect+the+English%22#v=snippet&q=%22Let%20not%20your%20studying%20the%20French%20make%20you%20neglect%20the%20English%22&f=false)"* (1760).
> 
> 
> *"Every advantage that … a complete knowledge of the Arabic could afford"* (1795).
> 
> 
> 

The OED says people use "*the*" with languages in an [elliptical](https://www.thefreedictionary.com/elliptical) way – that is, they’re mentally deleting part of a longer phrase. Examples: "translated from the Spanish [version]" … or "from the [original] German" or "from the Japanese [language]."

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[According to an online article](http://masteringarticles.com/definite-article-languages/#:%7E:text=Rule%207.12%3A%20Use%20the%20definite,The%20English%20language%20is%20hard):

> 
> Rule 7.12: Use the definite article when the word *language* immediately
> follows the name of a language.
> 
> 
> 
> > 
> > English is hard.
> > 
> > 
> > The English language
> > is hard.
> > 
> > 
> > 
> 
> 
> 
> > 
> > Bill wants to learn Chinese.
> > 
> > 
> > Bill wants to learn the Chinese language.
> > 
> > 
> > 
> 
> 
>