正常來說一句簡單的句子是只可以有一個動詞 (verb)。
e.g he is a boy.
He lives in Hong Kong.
可是如果中間有連接詞 (即 and, when, moreover, also etc.)就可以把兩句簡單的句子連在一起,成了一句比較復雜﹑多內容的句子。在這個情況下,一句句子就可以有兩個動詞。e.g. He is a boy and lives in Hong Kong for two years.
(在這裡,and 做了一個"勾"把兩句句子連起來)