情态动词与虚拟语气精讲 语气、推测与非真实条件的表达 2027届高三英语一轮复习专项讲义 情态动词表达说话人对动作或状态的推测、态度与评价，虚拟语气则用来表达假设、愿望等与事实不符的情况。二者常常交织出现，是高考语法填空、完形填空和写作中体现语言精准度的关键考点。 Part One：情态动词 1. 情态动词的基本特征 没有人称和数的变化，主语无论单复数，情态动词形式不变。 后面必须接动词原形（need、dare 作实义动词时除外）。 否定式直接在情态动词后加 not，疑问式将情态动词提前。 多数情态动词没有过去式、将来式、完成式的独立形式，需借助其他结构表达（如 be able to 代替 can 的将来式）。 2. 情态动词表能力、许可、请求 情态动词 用法 例句 can/could 能力（现在/过去）；请求（could 更委婉） Could you please turn down the music a little may/might 请求许可；might 更委婉、更不确定 You may leave the meeting early if necessary. be able to 强调经过努力后具备某种能力，可用于各种时态 After months of training, she was finally able to run a full marathon. 3. 情态动词表义务、必要性 情态动词 语气强度 例句 must 主观强制，语气最强，常表说话人自己的判断 You must hand in the application before Friday. have to 客观需要，强调外部规定或环境要求 Passengers have to show their ID cards at the checkpoint. should/ought to 理应、建议，语气较委婉 You should apologize to her for being late. need 有必要（否定式 needn't 表“不必”） You needn't bring your own laptop; one will be provided. 1) Visitors must not touch the exhibits in the museum. 参观者禁止触摸博物馆内的展品。 （must not 表禁止，语气强烈，不同于 needn't（不必）） 2) You needn't have rushed; the train was delayed by twenty minutes anyway. 你本不必那么匆忙的，反正火车晚点了二十分钟。 （needn't have done 表示“过去做了没有必要的事”，与实际做法相反） 4. 情态动词表推测———按肯定程度排序 结构 推测语气 例句 must + do/be doing 对现在情况把握较大的肯定推测 She must be at home now; the lights are on. can/could + do 用于疑问句、否定句表推测，肯定句少用 Can this rumor possibly be true may/might + do 不太确定的推测，might 比 may 更不确定 He might be stuck in traffic; that's why he's late. can't/couldn't + do 肯定的否定推测（不可能……） She can't be over thirty; she looks so young. 5. 情态动词 + 完成式———对过去情况的推测与评价 情态动词 + have done 结构，表示说话人站在现在的角度，对过去已发生的事情进行推测或评价。这是高考语法填空的高频考点。 结构 含义 例句 must have done （对过去）一定做过…… The ground is wet — it must have rained last night. can't/couldn't have done （对过去）不可能做过…… He can't have said that; he's always so polite. may/might have done （对过去）可能做过…… She might have forgotten our appointment. should/ought to have done 本应该做而实际没做（含责备、遗憾） You should have called me before coming; I wasn't home. shouldn't have done 本不应该做而实际做了（含责备、后悔） I shouldn't have eaten so much at the party. needn't have done 本不必做而实际做了（结果证明是多余的） You needn't have bought so much food for just the two of us. 1) You should have told me about the change of plan earlier. 你本应该早点告诉我计划有变的。 （shou ... ...
