fleet [fli:t] adj.快速的 vt.消磨 vi.疾驰;飞逝;掠过
(类)fleeting·pass=meteoric·rise 疾驰的·通过=流星似的·升起(快速对行为)
flexible [5fleksIbl] adj. 有弹性的;柔韧的;灵活的
(类)limber·flexibility=spindly·frailty 易弯曲的·柔韧性=细长的·脆弱
static·moving=pliable·inflexible 静止的·移动的=易弯的·不可弯曲的
flexibility·spinelessness=courage·daredevilry=courage·foolhardiness
柔韧性·没骨气=勇气·冒失(正常和过分关系)
(反)flexible ◆ mulish 灵活的 ◆ 和骡子一样固执的
flexibility ◆ calcification 柔韧 ◆ 僵化
flight [ flait ] n. 逃跑，溃退(an act or instance of running away)
flinch [flIntF] n.v.畏缩;退缩(to recoil, as from something unpleasant or difficult;shrink)
(类)grisly·flinch=droll·laugh 恐怖的·畏缩·好笑的·笑 (动作及其引发原因)
flinch·fear=grimace·pain 畏缩·害怕=痛苦的表情·疼痛(动作表达心理)
(记)区别：filch 偷窃;filth 污秽;finch 雀类
flippancy [`flIpEnsI] n. 轻率，无礼
(类)flip·respect=nonchalant·concern 无礼的·尊重=冷漠的·关心(反面特征)
(反)flippancy ◆ earnest/gravity/seriousness/sobriety 轻率 ◆ 认真,庄重,冷静