Fiesta
Finish is another word for completion starting with the letter F.
front
Frail.
fierceness, fury
flatten
fleet-footed
Flirting
The opposite for the word plain starting with letter f is FANCY.
Floccinaucinihilipilification is the longest word starting with F; it means the act of estimating something as worthless.
One word for being late starting with the letter F is forgot.
favor, favorite,
family