By the way, the articles in English, like in German, Dutch, Danish, French, Spanish, Greek, Arabic, Hebrew, and so on, come from demonstrative pronouns or number words. English is a typical late Indo-European language, and Late Indo-European languages have tended to develop articles, because earlier on, they had a lot of case endings.

See, over time, as the sound changed, the case endings wore off or got confused, and using a demonstrative pronoun or a number together with a noun was the strategy speakers used to make the gender or case of a noun more obvious when the noun’s own ending couldn’t do the job.

“The” is a worn-down version of “that” and “an” is a worn down version of an old pronunciation of “one.” English doesn’t have case endings at all anymore, but the articles still stay around as a way of saying “Hey, what follows is a noun.”