المعنى الاصطلاحي

Infinite time into the future.

الشرح المختصر

"Abad" (eternity) is the perpetual existence of something along endless ages in the future. Its opposite is "azal", which means perpetual existence of something along endless time in the past. The concept of "abad" (eternity) falls under two sections: 1- Eternity of Allah Almighty and His Attributes. 2- Eternity of some created beings such as the people of Paradise and the people of Hell. There is difference between the two: Firstly: the eternity of Allah Almighty is an intrinsic attribute, whereas the eternity of others is acquired by a permission of Allah. Secondly: the eternity of Allah Almighty is in the most perfect manner, and befits His glory and magnificence. However, a created being that could reach a limit of eternity, it is inferior to that of Allah Almighty. Thirdly: the eternity of Allah, the Exalted, is essential, whereas the eternity of others is possible. Fourthly: the eternity of Allah Almighty is not preceded by nonexistence or followed by nonexistence, unlike the created beings, as they will undergo death, even though they will be resurrected thereafter.

التعريف اللغوي المختصر

"Abad": infinite long time, perpetual, pre-existent, pre-eternal.