function
She attended a charity function and made a generous donation.
The word event could be substituted for function and the meaning of the sentence would not change,
Forceless or Failing
Flexible
fool
The word is fantasy.
foolproof
fetch
friction
fatal
Flicker.
fax
Friable means easily crumbled or broken.
"Flamboyant" is a fun word to say that means elaborate. "Flashy" is a simpler word that means the same thing.