F
fall back on 求助于
fall behind 落后
familiar with 熟悉
few and far between 很少,很稀疏
figure out 弄清楚,算出,想出
fill the prescription 按照药方配药
find fault with 挑剔,抱怨
flat tyre 轮胎没气了
for the time being 暂时
for sale 待售
focus on 集中在
for a change 为了换换花样
for a time 暂时,一度
for ages 很久
for free 免费
for good 永久的
for the time being 暂时
free with money 花钱大手大脚
from bad to worse 每况愈下
from time to time 时常