- fallacious: LOGICALLY UNSOUND; MISLEADING
- fallible: LIABLE TO ERR
- fallow: PLOWED BUT NOT SOWED; UNCULTIVATED
- falter: HESITATE
- fanaticism: EXCESSIVE ZEAL
- fanciful: WHIMSICAL; VISIONARY
- fastidious: DIFFICULT TO PLEASE; SQUEAMISH
- fatalism: BELIEF THAT EVENTS ARE DETERMINED BY FORCES BEYOND ONE'S CONTROL
- fatuous: FOOLISH; INANE
- fawning: COURTING FAVOR BY CRINGING AND FLATTERING
- feasible: PRACTICAL
- fecundity: FERTILITY; FRUITFULNESS
- feign: PRETEND
- feint: TRICK; SHIN; SHAM BLOW
- felicitous: APT; SUITABLY EXPRESSED; WELL CHOSEN
- ferment: AGITATION; COMMOTION