formar, to form, compose, fall in.
fórmula, formula, prescribed rule.
fornido, strong, sturdy.
forraje, m., forage, grain, hay, grass.
forrar, to line, upholster.
fortaleza, fortress.
fortuna, fortune, success.
fósforo, match.
foso, ditch, moat.
frac, m., dress-coat, evening coat.