be fly
fly 作形容词时通常用作表语，多见于英式非正式口语，指人精明、不易上当。
Don't try to trick him—he's fly.
别想骗他——他机灵得很。
机灵的；不易上当的；敏捷的
clever and not easily tricked or deceived; shrewd
英式非正式用法，多形容人精明、不易被骗。
机灵的；不易上当的
(British informal) not to be deceived or hoodwinked
He's a fly old bird who never falls for cheap tricks.
他是个机灵的老头，从不上廉价把戏的当。
用法提示：fly 作形容词，修饰 old bird，表示机灵、不易上当。
You won't fool her; she's too fly for that.
你骗不了她；她太机灵了，不会上那个当。
用法提示：fly 作形容词，在 too...for 结构中表示机灵、不易被骗。
Even as a child, she was fly enough to see through his lies.
甚至还是个孩子的时候，她就够机灵，能看穿他的谎言。
用法提示：fly 作形容词，与 enough to 连用，表示机灵得足以识破谎言。
fly 作形容词时通常用作表语，多见于英式非正式口语，指人精明、不易上当。
Don't try to trick him—he's fly.
别想骗他——他机灵得很。
too...to 结构表示“太……以致不会……”，此处 fly 说明人不易受骗。
She was too fly to believe that excuse.
她太机灵了，不会相信那个借口。
fly enough to do sth 表示“精明到足以做某事”，一般用于肯定句。
He's fly enough to see through the scam.
他够精明，能识破这个骗局。
grammar · medium
易错句子He very fly, so nobody can cheat him.
正确表达He is very fly, so nobody can cheat him.
fly 作形容词表示“机灵的、不易上当的”，是表语形容词，必须和 be 动词连用构成系表结构。汉语“他很机灵”用形容词直接作谓语，不需要系动词，学生因此常漏掉 is。补上 is 后句子才符合英语语法。
grammar · medium
易错句子He is a fly, so nobody dares to cheat him.
正确表达He is fly, so nobody dares to cheat him.
这里要表达的是“他很机灵”，fly 是形容词，作表语时前面不能加冠词。加上 a 之后，fly 就变成名词，意思是“一只苍蝇”，句子意思完全跑偏。汉语没有冠词，学生容易在形容词前误加 a/an，去掉 a 即可。
太机灵，骗不到
He thinks he can trick her, but she's too fly to be fooled.
他以为能骗到她，可她太机灵了，骗不到。
机灵得能看穿
She was fly enough to see through the whole scam.
她够机灵，看穿了整个骗局。
精明的家伙
Mind what you say — he's a fly customer.
说话小心点——他是个精明的家伙。
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