Al Jaami'

Jamaʿa is gathering up what had been spread apart — the root behind jumuʿa, the day of gathering, behind jamīʿ, all together, and behind the plural itself. Arabic makes its plurals out of a word for reassembling things.

This definite form is not in the Qur’an; the word without its article is there three times, and the first of them is a sentence addressed to God rather than about Him: You are the gatherer of people for a day about which there is no doubt. It is said inside a prayer, by people asking not to be let go of. What has been separated is not necessarily separated for good.