fōns (font-), a spring: font, fount, fountain (Fr.), fontal.
fōrm-a, shape; form-o (formāt-), I shape: form, formal, formula, perform.
forti-s, steadfast, brave: forti-tude, fortify; through Fr., comfort, effort, force, forte, fort, fortress.
frag-, frang-o (fract-), I break: fragile, fragment, fracture, in-fringe.
frāter, brother: fraternal, fraternity, fratricide (caedo), friar (Fr.).
frīgidus, be cold; frīger-are, make cold: frigidity, refrigerate, refrigerant.
frons (front-), forehead: front, frontal, affront, effrontery and frontier.
frūg-, fru-i (fruct-), to enjoy; frūg-es, fructus, fruit; frugi, useful: fructify, frugi-ferous, frugi-vorous, fruit, fruition, frugal.
fŭgi-o (fŭgit-), I flee: fugitive, refuge, subterfuge, febrifuge (febris, fever).