The pronunciation between /w / 和/v/ /w/和/v/

这两音的主要区别就在于发/v/音时的主要特别是上牙轻触下嘴唇，然后让气流冲开发音。
而发/w/时唇齿是不接触的，特别注意发音时嘴形是圆。

Say this tongue twisters and sayings out loud to practice the sounds [w] [v] :

Woodson's waistcoat is weirdly vented.
Wise women don't walk in the woods while wolves wander.
Vivian, Valerie and Virginia verbally voiced vivid salvos.
Walls have ears.
Visits always give pleasure.
Well fed, well bred.