Merriam-Webster's Collegiate Dictionary:
realism
realist
realistic
realistically
reality
reality check
realizable
realization
realize
realizer
really
realm
realness
realpolitik
realtor
realty
ream
reamer
reap
reaper
reaphook
reapportion
reapportionment
rear
rear admiral
rear admiral (lower half)
rear admiral (upper half)
rear echelon
rear end
rear guard
rear-end
rearer
rearguard
rearm
rearmament
rearmost
rearview mirror
rearward
rearwards
reas
reason
reasonability
reasonable
reasonableness
reasonably
reasoner
reasoning
reasonless
reasonlessly
reassurance
reassure
reassuringly
reata
reaumur
reave
reaver
reb
rebar
rebarbative
rebarbatively
rebate
rebater
rebato
rebbe
rebec
rebeck
rebekah
rebel
rebel yell
rebellion
rebellious
rebelliously
rebelliousness
rebild
rebirth
reblochon
reboant
reborn
rebound
rebounder
rebozo
rebranch
rebroadcast
rebuff
rebuild
rebuke
rebuker
rebus
rebut
rebuttable
rebuttal
rebutter
rec
rec room
rec'd
recalcitrance
recalcitrancy
