1. 在其系表结构后接不定式时，句子主语只能是形式主语it, 而不能是指人或指物的名词或代词等。如：
我们可能(不可能) 会赢得这场比赛。
正：It is possible (impossible) for us to win the match.
误：We are possible (impossible) to win the match.
若其后不定式与句子主语有动宾关系，则 impossible 则可以不用形式主语 it 而用名词作主语，但possible不能（或很少）这样用。如：
正：The match is impossible for us to win.
误：The match is possible for us to win.
2. 若 be possible (impossible) 后不接不定式或从句，则完全可以用“物”作主语。如：
Snow is possible, though not probable. 下雪是可能的，虽然不是很可能
单词：impossible的近义词、反义词、形近词辨析
impossible/possible/possibly/possibility/probable/probably/likely/unlikely/maybe/perhaps/potential
记忆：
1. possible [ 5pCsEbl ] poss-ible, adj. 可能的 It’s possible for him to lose heart after the defeat.他失败后可能会灰心。
2. impossible [ im5pCsEbl ] adj. 不可能的 It’s impossible that he failed again!他怎么会又失败了！
3. possibly [ 5pCsEbli ] adv. 可能 Possibly, we can send up another manned spacecraft next year.明年我们有可能再次发射载人太空飞船。
4. possibility [ 7pCsi5biliti ] n. 可能性 There lies the possibility that the earth will be overcrowded with human beings.地球有可被过多的人类挤满了。
5. probable [ 5prCbEbl ] adj. 很可能的, 大概的 We had to prepare for the probable heavy rain.我们得为可能的大雨作好准备。
6. probably [5prRbEb(E)lI] adv. 很可能地, 大概地 Mr. Wang is probably his long lost brother!王先生可能就是他失散多年的兄弟！
7. likely [ 5laikli] adj. 很可能的 注意：可以说 Somebody is likely to do something (possible, probable 则不可) Mr. Wang is likely to be his long lost brother.王先生可能就是他失散多年的兄弟。
8. unlikely [ Qn5laikli] adj. 未必的, 不太可能的 It’s unlikely that the Middle East will embrace peace with Israel’s Unilateral action plan.以色列的单边行动计划不可能给中东带来和平。
9. maybe [ 5meibi ] adv. 大概, 或许 Maybe you are right.或许你是对的。
10. perhaps [ pE5hAps ] adv. 或许, 多半 Perhaps it will be another fine day.多半又是一个好天气。
11. potential [pE5tenF(E)l] Capable of being but not yet in existence adj. 潜在的, 可能的 We will develop our potential power.我们将开发我们的潜在能力。
另类阅读：
It’s impossible for Chen Shuibian to separate Taiwan from the mainland. The mainland is unlikely to allow its independence. China must unite. There lies the possibility that a war will probably happen across the straits, and perhaps the USA will stand on the side of Chen Shuibian, China will take Taiwan back at any cost.
与单词：impossible 相关的例句或者名人名言
It is impossible for me to win this game.
我不可能赢这场游戏。
This vast desert looks impossible to pass.
这片辽阔的沙漠看上去不可能穿越。
It is impossible to establish democracy amid economic chaos.
在经济混乱时期建立民主国家是不可能。
It is impossible to get there before ten.
10点钟以前到那儿是不可能的。
※It is impossible that a man who is false to his friends should be true to his country. 对朋友不义，不可能对国家效忠。
※It is impossible to defeat an ignorant man in argument. ( W. G. McAdoo )—— 在争论中是无法击败无知者的。（麦卡杜）
