All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The word Abadan (for ever) in the Arabic language means eternity without an end, and this differs from the word Khulood (staying for a long time) which does not necessarily mean eternity but means a long time. It is for this reason that Allaah mentioned both meanings in several verses in the Quran and this proves that they have different meanings otherwise this would be just repetition, and this is contrary to the principle (which reads that coupling between two words indicates a change in meaning) as stated by Ar-Raazi in his Tafseer (interpretation of the Quran). For more benefit, please refer to Fatwa 90244.
Allaah Knows best.