5 letter words:
firns8,
ruins5,
4 letter words:
fins7,
firn7,
firs7,
funs7,
furs7,
rifs7,
surf7,
rins4,
ruin4,
runs4,
urns4,
3 letter words:
fin6,
fir6,
fun6,
fur6,
ifs6,
rif6,
ins3,
nus3,
rin3,
run3,
sin3,
sir3,
sri3,
sun3,
uns3,
urn3,
2 letter words:
if5,
in2,
is2,
nu2,
si2,
un2,
us2,