6 letter words:
niffer12,
5 letter words:
fifer11,
finer8,
infer8,
4 letter words:
fief10,
fife10,
riff10,
fern7,
fine7,
fire7,
firn7,
neif7,
reif7,
rife7,
rein4,
3 letter words:
eff9,
iff9,
fen6,
fer6,
fie6,
fin6,
fir6,
ref6,
rif6,
ern3,
ire3,
rei3,
rin3,
2 letter words:
ef5,
fe5,
if5,
en2,
er2,
in2,
ne2,
re2,