Root ر د ف(r d f) has 3 unique word forms and appears 3 times in the Quran.

English gloss Follow, Succeed, Follow one another, Synonymous

Word Translation Occurrences
رَدِفَ close behind, close behind 2
ٱلرَّادِفَةُ the subsequent, the subsequent 2
مُرۡدِفِينَ one after another, one after another 2