In northern Australia, different shells were used by different tribes, one tribe's shell often being quite worthless in the eyes of another tribe. format formation formative former formerly formidable formidably formless form letter formula formulae formulate formulation fornicate fornication forsake forsaken forsook forswear forswore forsworn fort forte forth forthcoming forthright fortieth fortification fortify fortitude fortress fortuitous fortunate fortunately fortune fortune cookie fortune teller forty forum forward forwarding address forward-looking forwards forwent fossil fossil fuel fossilize foster fought foul foul ball foul play found foundation founder founding father foundry fountain fountain pen four four-leaf clover four-letter word fourteen fourteenth fourth fourthly Fourth of July four-wheel drive fowl fox foxhole foxtrot foxy foyer fracas fraction fractional fractionally fractious fracture fragile fragility fragment fragrance fragrant frail frailty frame framework franc franchise frank frankfurter frankly frankness frantic frantically frat fraternal fraternity fraternize fraud fraudulent fraudulently fraught fray freak freak out freckle freckled free freebie freedom free enterprise free-for-all freehand freelance freelancer freeload freeloader freely free market free-range free speech freethinker freethinking freeway format formation formative former formerly formidable formidably formless form letter formula formulae formulate formulation fornicate fornication forsake forsaken forsook forswear forswore forsworn fort forte forth forthcoming forthright fortieth fortification fortify fortitude fortress fortuitous fortunate fortunately fortune fortune cookie fortune teller forty forum forward forwarding address forward-looking forwards forwent fossil fossil fuel fossilize foster fought foul foul ball foul play found foundation founder founding father foundry fountain fountain pen four four-leaf clover four-letter word fourteen fourteenth fourth fourthly Fourth of July four-wheel drive fowl fox foxhole foxtrot foxy foyer fracas fraction fractional fractionally fractious fracture fragile fragility fragment fragrance fragrant frail frailty frame framework franc franchise frank frankfurter frankly frankness frantic frantically frat fraternal fraternity fraternize fraud fraudulent fraudulently fraught fray freak freak out freckle freckled free freebie freedom free enterprise free-for-all freehand freelance freelancer freeload freeloader freely free market free-range free speech freethinker freethinking freeway issue commodity receipts term inclusive instruments tribes quite worthless being