free - gas
- free argument
- free bubble
- free carrier
- free charge
- free electron
- free energy
- free energy level
- free exiton
- free field
- free grid
- free hole
- free impedance
- free magnetic pole
- free net
- free oscillation
- free path
- free period
- free plasma
- free progressive wave
- free reel
- free space
- free time
- free vibration
- free wave
- free-air cone resonance
- free-air ionization chamber
- free-block queue
- free-carrier absorption
- free-carrier plasma
- free-electron approximation
- free-electron laser
- free-electron mass
- free-electron paramagnetism
- free-electron scattering
- free-field response
- free-free transition radiation
- free-hole scattering
- free-ion spin
- free-line signal
- free-point tube tester
