A Word Quiz

What do these words have in common - apart from having four letters?

ABLE
ACED
ACES
AILS
AINT
AIRS
ARMS
EARS
EAST
EATS
EELS
EWER
IRES
LAGS
LAIR
LAKE
LAME
LANK
LAPS
LASH
LAWS
LAYS
LEAS
LEER
LEES
LICK
LIES
LINT
LIPS
LOGS
LOUT
LOWS
LUFF
LUKE
OILS
OLIO
OURS
OWLS
RAGS
RAIL
RANK
RAYS
REED
RILL
RISK
RITZ
ROCK
RUMP
USED
USES

Answer:

Each one forms another ordinary word, with a different meaning, by the addition of the same initial letter, F.

FABLE
FACED
FACES
FAILS
FAINT
FAIRS
FARMS
FEARS
FEAST
FEATS
FEELS
FEWER
FIRES
FLAGS
FLAIR
FLAKE
FLAME
FLANK
FLAPS
FLASH
FLAWS
FLAYS
FLEAS
FLEER
FLEES
FLICK
FLIES
FLINT
FLIPS
FLOGS
FLOUT
FLOWS
FLUFF
FLUKE
FOILS
FOLIO
FOURS
FOWLS
FRAGS
FRAIL
FRANK
FRAYS
FREED
FRILL
FRISK
FRITZ
FROCK
FRUMP
FUSED
FUSES