regularisation vs. regularization
ruggedisation vs. ruggedization
reinforcement vs. strengthener
reenforcement vs. reinforcement
randomisation vs. randomization
rationalization vs. systematization
rationalisation vs. rationalization
rationalisation vs. systematization
republication vs. republishing
reallotment vs. reapportionment
responsibility vs. responsibleness
redeployment vs. redisposition
remilitarisation vs. remilitarization
romanticization vs. sentimentalization