- free radical damage
- free radical isomerization polymerization
- free radical lifetime
- free radical metabolism
- free radical polymerization
- free random walk
- free range
- free range raising
- free-reed flute
- free resolution
- free ribosome
- free rider problem
- free ring
- free rootstock
- free rotation
- free school
- free Schroder path
- free scientific research theory in law
- free semester system
- free semigroup
- free set
- free settling
- free settling lamination theory
- free settling terminal velocity
- free sheaf