watch是动词原形，用于第一、第二人称或复数的句子中，如they watch football game every week.watches是第三人称单数形式，主要用于第三人称单数作主语的情况，如she watches football game every week.
watch用法例句
In spite of the watch set on the house,the thief escaped.
尽管这幢房子设置了看守人员，小偷还是逃跑了。
The shepherds watched their flocks.
牧羊人看守着自己的羊群。
I could sit and watch the river all day long.
我可以整天坐在这里看那条河。
You need to reset your watch to local time.
你需要把表调整到当地时间。
By my watch it is two o'clock.
我的表是两点钟。