這種句型主要用來表示主語的特點、身份等.其系動詞一般可分為下列兩類：
(1)表示狀態(tài).這樣的詞有：be, look, seem, smell, taste, sound, keep等.如：
1) This kind of food tastes delicious.這種食物吃起來很可口.
2) He looked worried just now.剛才他看上去有些焦急.
(2)表示變化.這類系動詞有：become, turn, get, grow, go等.如：
1) Spring comes. It is getting warmer and warmer.春天到了,天氣變得越來越暖和.
2) The tree has grown much taller than before.這棵樹比以前長得高多了.