請問[比較式]英文點用?

只用big一個既時候, 就係形容詞
eg: Today i have bought a big and fresh water-lemon.
用bigger既時候就係.. 2樣事物之間既比較
例如A物件係一隻cat, B物件係一隻mouse
你當然知道cat係比mouse大隻好多la
所以你就話the cat is bigger than the mouse (cat比mouse仲大隻)
biggest就係幾樣事物之間既比較.. (多過2樣)
係A,B,C之中..
C係最長的
(C is the longest among a,b and c) 物件c係a,b,c中係最長的

"A" is bigger than "B"
"C" is the biggest among "A", "B" and "C"

anymore questions?