(每日一词）wag

Wag  /wæɡ/ v. （使）（尤指尾巴或手指）摆动，摇

meaning: (especially of a tail or finger) to move from side to side or up and down, especially quickly and repeatedly, or to cause this to happen.

1) 对比：wag--bag 

2) 联系：w--wave, w—弯曲

e.g. The little dog’s tail wagged in delight. 那条小狗欢快地摇着尾巴。