frecuentar - to frequent
frenar - to break, to slow down, to restrain
fruncir - to wrinkle, to pucker, to knit
fumigar - to fumigate
fundar - to found, to base
fundir - to melt
fungir - to act (as)
festejarse - to enjoy one's self
fraccionar - break, dissipate
fisgar - pry
facultar - authorize, empower
filtrar - percolate
fortificar - fortify