发音
上齿轻触下唇
声带不震动

单词
face fact fail
fall family far
feel few find
safe self staff
first follow for
brief chief relief
forget form from
offer office often
after before forever
enough laugh tough

句子
I feel safe.
We should follow way.
The first offer is good.
The family are from France.
There is enough room in the office.

同音
flew flu
for four
fin Finn
fair fare
feet feat
few phew
flour flower
foul fowl
forth fourth

辨音
[f] [v]
fan van
fat vat
fast vast
file vile
ferry very
leaf leave
life live
safe save
belief believe
proof prove