(س) رَدِفَ يَرْدَفُ رَدْفًاradifa yardafu radfan: to come behind, to ride behind someone on a mount. ﴿عَسٰٓى اَنْ يَّكُوْنَ رَدِفَ لَكُمْ﴾ (An-Naml 27:72)
رَادِفَةٌrādifah (feminine active participle, ism fāʿil): that which follows — i.e. the second blast of the Trumpet, which will come after the first. ﴿تَتْبَعُهَا الرَّادِفَةُ﴾ (An-Nāziʿāt 79:7)
Form IV (ifʿāl) اَرْدَفَ يُرْدِفُ اِرْدَافًاardafa yurdifu irdāfan: to make follow behind; مُرْدِفٌmurdif pl. مُرْدِفِيْنَmurdifīna (active participle, ism fāʿil): coming one after another, in succession. ﴿بِاَلْفٍ مِّنَ الْمَلٰٓئِكَةِ مُرْدِفِيْنَ﴾ (Al-Anfāl 8:9). This root occurs three times in the Quran.
Form VI (tafāʿul) تَرَادَفَ يَتَرَادَفُ تَرَادُفًاtarādafa yatarādafu tarādufan: to follow one after another; (of words) to be synonymous (this verb is not used in the Quran).