Steam
soot
Another word for opportunity which begins with 'S' is scope.
bias
One word would be "prince". Add an -s and you have the plural - "princes". Add another -s and you have "princess", a word in singular form.
softening
shelter
screwdriver
scoundrel
Supervisor
Sensational!
Irks
* short, slight
skein
stupendous
Sharp or spirited.
sports
despises