twice 两倍
twice as...as... 像…的两倍…

She's twice as old as me.
她的年纪比我大一倍。/ 她的年纪是我的两倍。

The state is twice as big as England.
这个州是英格兰的两倍大。
state （美国、澳大利亚、德国等）州，邦

除了 twice as big as...（面积、体积）是…两倍大
twice as old as... 年纪是…的两倍
也常会说 
twice as good as... 是…的两倍好
twice as hard as... 是…的两倍困难

half 一半，半个
half as...as... 像…的一半…

She's half as old as me.
她的年纪只是我的一半。

The state is half as big as England.
这个州是英格兰的一半大。

He's half as interesting as you.
他只有你一半有趣。
as interesting as you 像你一样有趣
half as interesting as you 像你一半有趣，（只）有你一半有趣

He's half as good as you.
他只有你一半好。