{"id":7473,"date":"2026-07-15T09:07:46","date_gmt":"2026-07-15T09:07:46","guid":{"rendered":"https:\/\/18kenglish.com\/?p=7473"},"modified":"2026-07-15T09:09:23","modified_gmt":"2026-07-15T09:09:23","slug":"%e5%8a%a9%e5%8b%95%e8%a9%9e-modal-auxiliary-verbs","status":"publish","type":"post","link":"https:\/\/18kenglish.com\/th\/%e5%8a%a9%e5%8b%95%e8%a9%9e-modal-auxiliary-verbs\/","title":{"rendered":"\u52a9\u52d5\u8a5e\u7528\u6cd5\u5b8c\u6574\u653b\u7565\uff1a10 \u500b\u5fc5\u5b78\u82f1\u6587\u52a9\u52d5\u8a5e | Auxiliary & Modal Verbs"},"content":{"rendered":"
\nQuick Answer\uff08\u5feb\u901f\u89e3\u7b54\uff09\uff1a<\/strong> \u52a9\u52d5\u8a5e\uff08auxiliary verbs\uff09\u662f\u5e6b\u52a9\u4e3b\u8981\u52d5\u8a5e\u69cb\u6210\u554f\u53e5\u3001\u5426\u5b9a\u53e5\u3001\u6642\u614b\u548c\u8a9e\u6c23\u7684\u52d5\u8a5e\u3002\u82f1\u6587\u52a9\u52d5\u8a5e\u5206\u6210\u5169\u5927\u985e\uff1a\u4e3b\u8981\u52a9\u52d5\u8a5e<\/strong>\uff08primary auxiliaries \u2014 be\u3001do\u3001have\uff09\u548c\u60c5\u614b\u52a9\u52d5\u8a5e<\/strong>\uff08modal auxiliaries \u2014 can\u3001could\u3001will\u3001would\u3001shall\u3001should\u3001may\u3001might\u3001must\uff09\u3002\u4e3b\u8981\u52a9\u52d5\u8a5e\u8ca0\u8cac\u6587\u6cd5\u7d50\u69cb\uff0c\u60c5\u614b\u52a9\u52d5\u8a5e\u8ca0\u8cac\u8868\u9054\u53ef\u80fd\u6027\u3001\u80fd\u529b\u3001\u7fa9\u52d9\u548c\u8a31\u53ef\u3002\u638c\u63e1\u9019 10 \u500b\u52a9\u52d5\u8a5e\uff0c\u4f60\u5c31\u80fd\u7d44\u51fa 90% \u7684\u65e5\u5e38\u82f1\u6587\u53e5\u5b50\u3002\n<\/div>\n

Here is a number that surprises most of my students in Taipei: the single most common verb in written English is not “have” or “go” \u2014 it is “be”, and roughly one in four times you see it, it is working as a helper, not a main verb. That helper role is exactly what \u52a9\u52d5\u8a5e do. They are the small, unglamorous words that decide whether a sentence is a question, a denial, a fact, or a polite request \u2014 and Taiwanese learners lose more points on them than on any flashy vocabulary word.<\/p>\n

\"English<\/p>\n

The rules are short. The practice is what makes them automatic.<\/em><\/p>\n

\u4ec0\u9ebc\u662f\u52a9\u52d5\u8a5e\uff1f(What Are Auxiliary Verbs?)<\/h2>\n

\u52a9\u52d5\u8a5e are verbs that “assist” a main verb. On their own they carry very little meaning; their job is to add grammatical information \u2014 tense, negation, questions, voice, or attitude. In the sentence “She \u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16<\/strong> swim,” the real action is “swim”. “Can” is the auxiliary verb, and it tells you she has the ability. Strip the helper away and “She swim” is broken. That is the whole point: the auxiliary is what makes the grammar legal.<\/p>\n

English has a fixed, small set of them, and that is good news. Unlike vocabulary, which is effectively infinite, the list of \u52a9\u52d5\u8a5e fits on an index card. There are three primary auxiliaries and nine common modal auxiliaries. Learn those twelve words and how they behave, and you have covered the machinery behind nearly every question, negative, and shade of politeness in the language.<\/p>\n

One rule ties them all together and it is worth memorising before anything else: an auxiliary verb is always followed by another verb<\/strong> (or clearly implies one). “Do you like coffee?” \u2014 “do” helps “like”. “I must leave.” \u2014 “must” helps “leave”. If there is no second verb hiding somewhere, the word is probably not acting as an auxiliary at all.<\/p>\n

\u52a9\u52d5\u8a5e\u7684\u5169\u5927\u5206\u985e (The Two Types of Auxiliary Verbs)<\/h2>\n

Every \u52a9\u52d5\u8a5e falls into one of two families, and confusing the two is the root of most mistakes I see. Primary auxiliaries build the plumbing of a sentence \u2014 they form tenses, questions, and negatives. Modal auxiliaries add human judgement \u2014 ability, permission, obligation, probability. Here is the split at a glance:<\/p>\n\n\n\n\n\n\n
\u985e\u578b (Type)<\/th>\n\u52a9\u52d5\u8a5e (Verbs)<\/th>\n\u4e3b\u8981\u529f\u80fd (Main Job)<\/th>\n<\/tr>\n<\/thead>\n
\u4e3b\u8981\u52a9\u52d5\u8a5e<\/strong>
Primary auxiliaries<\/td>\n		be, do, have<\/td>\nForm tenses, questions, negatives, and the passive voice (\u88ab\u52d5\u8a9e\u614b)<\/td>\n<\/tr>\n
\u60c5\u614b\u52a9\u52d5\u8a5e<\/strong>
Modal auxiliaries<\/td>\n		can, could, will, would, shall, should, may, might, must<\/td>\nExpress ability, permission, obligation, and probability<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The practical difference: primary auxiliaries change their form (I am<\/em>, she \u0e40\u0e1b\u0e47\u0e19<\/em>, they were<\/em>; I do<\/em>, he does<\/em>). Modal auxiliaries never do \u2014 “he can”, not “he cans”. That one habit, adding an “s” to a modal, is the single most common error in Taiwanese student writing, and we will come back to it.<\/p>\n

\"Taiwan<\/p>\n

Most Taiwan classrooms teach modal verbs as a vocabulary list. They work better as a system.<\/em><\/p>\n

be\u3001do\u3001have\uff1a\u4e09\u500b\u4e3b\u8981\u52a9\u52d5\u8a5e (The Three Primary Auxiliaries)<\/h2>\n

The tricky thing about be, do, and have is that each one lives a double life. Each can be a full main verb \u0e41\u0e25\u0e30<\/em> an auxiliary, and Taiwanese learners often can’t tell which hat it is wearing. The test is simple: if there is a second verb after it, it is an auxiliary.<\/p>\n

Be<\/strong> as an auxiliary builds continuous tenses and the passive voice. “She \u0e40\u0e1b\u0e47\u0e19<\/strong> studying” (continuous). “The report was<\/strong> written by the intern” (passive \u2014 \u88ab\u52d5\u8a9e\u614b). Compare that with “She \u0e40\u0e1b\u0e47\u0e19<\/strong> a teacher”, where “is” is the main verb and there is no second verb to help. Same word, two completely different jobs.<\/p>\n

Do<\/strong> is the question-and-negative machine of the present and past simple. English can’t ask “You like it?” in standard writing \u2014 it needs “Do<\/strong> you like it?” and “I \u0e2d\u0e22\u0e48\u0e32<\/strong> like it.” This “dummy do” has no meaning of its own; it exists purely so the sentence has an auxiliary to carry the question. Chinese has no equivalent, which is exactly why “You have breakfast already?” slips out so often.<\/p>\n

Have<\/strong> as an auxiliary builds the perfect tenses: “I have<\/strong> finished,” “She had<\/strong> left before noon.” Again, contrast the main-verb use in “I have<\/strong> a car,” where nothing follows to be helped. Get comfortable spotting the second verb and be\/do\/have stop being confusing overnight.<\/p>\n

\u60c5\u614b\u52a9\u52d5\u8a5e\u5b8c\u6574\u5217\u8868 (The Complete Modal Verb List)<\/h2>\n

Now the interesting family. \u60c5\u614b\u52a9\u52d5\u8a5e don’t change sentence structure \u2014 they change meaning and tone. The same event can sound like a certainty, a guess, an order, or a gentle suggestion depending only on which modal you choose. This table is the one I tell students to copy into their notebook:<\/p>\n\n\n\n\n\n\n\n\n\n
\u60c5\u614b\u52a9\u52d5\u8a5e<\/th>\n\u610f\u601d (Meaning)<\/th>\n\u4f8b\u53e5 (Example)<\/th>\n<\/tr>\n<\/thead>\n
can \/ could<\/td>\n\u80fd\u529b\u3001\u8a31\u53ef (ability, permission)<\/td>\nI \u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16<\/strong> speak three languages.<\/td>\n<\/tr>\n
will \/ would<\/td>\n\u672a\u4f86\u3001\u610f\u9858 (future, willingness)<\/td>\nI will<\/strong> email you tonight.<\/td>\n<\/tr>\n
shall \/ should<\/td>\n\u5efa\u8b70\u3001\u7fa9\u52d9 (advice, obligation)<\/td>\nYou should<\/strong> see a doctor.<\/td>\n<\/tr>\n
may \/ might<\/td>\n\u53ef\u80fd\u6027\u3001\u8a31\u53ef (possibility, permission)<\/td>\nIt might<\/strong> rain later.<\/td>\n<\/tr>\n
must<\/td>\n\u5f37\u70c8\u7fa9\u52d9\u3001\u63a8\u6e2c (strong obligation, deduction)<\/td>\nYou must<\/strong> wear a helmet.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Two rules govern all of them. First, a modal is always<\/em> followed by the base form of the verb \u2014 no “to”, no “-ing”, no “-s”. It is “She must \u0e44\u0e1b<\/strong>“, never “She must to go” or “She must goes”. Second, modals have no infinitive and no past participle of their own; when you need a past or future meaning, English swaps in a substitute like “was able to” or “had to”. “Yesterday I \u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16<\/strong> not sleep” works for ability, but for a single completed action you say “I was able to<\/strong> finish the report.”<\/p>\n

\"modal<\/p>\n

Write out your own example sentences \u2014 recognition is not the same as production.<\/em><\/p>\n

Notice the pairs \u2014 can\/could, will\/would, shall\/should, may\/might. The second word in each pair is not simply the past tense. More often it is the politer, softer, or more tentative<\/em> version. “Can you help?” is fine among friends; “Could you help?” is what you write to your boss. That politeness shift is worth more in a Taiwan workplace than any single vocabulary word, because it signals respect without changing what you are actually asking.<\/p>\n

\"English<\/p>\n

Ten minutes of focused review beats an hour of passive reading.<\/em><\/p>\n

\u53f0\u7063\u5b78\u751f\u6700\u5e38\u72af\u7684 5 \u500b\u52a9\u52d5\u8a5e\u932f\u8aa4 (5 Common Auxiliary Verb Mistakes)<\/h2>\n

After two decades of marking English homework in Taipei, the same five errors come up again and again. None of them are about intelligence \u2014 they are about the gap between Chinese and English structure. Fix these five and your writing jumps a level.<\/p>\n

1. Adding “-s” to a modal.<\/strong> “He cans swim” and “She musts leave” are the classic slips. Modals never take a third-person “-s”. The main verb doesn’t either: “He can swim”, full stop.<\/p>\n

2. Adding “to” after a modal.<\/strong> Chinese logic pushes learners toward “I must to study” and “We should to practice”. Every modal except “ought to” is followed by the bare base verb \u2014 drop the “to”.<\/p>\n

3. Doubling up auxiliaries.<\/strong> “Do you can help me?” stacks two auxiliaries where English allows only one per clause. The modal already forms the question, so it becomes “Can you help me?” No “do” needed.<\/p>\n

4. Forgetting “do” in questions and negatives.<\/strong> The mirror-image mistake: “You like coffee?” and “I not like it.” Present and past simple need the “do” auxiliary \u2014 “Do you like coffee?” and “I don’t like it.”<\/p>\n

5. Confusing “must not” with “don’t have to”.<\/strong> These feel similar but mean opposite things. “You must not park here” is a prohibition (\u7981\u6b62). “You don’t have to park here” means it is optional (\u4e0d\u9700\u8981). Mixing them up in an email can turn a friendly note into an order.<\/p>\n

\"studying<\/p>\n

You already use \u52a9\u52d5\u8a5e every time you ask a question in English.<\/em><\/p>\n

\u5982\u4f55\u5feb\u901f\u638c\u63e1\u52a9\u52d5\u8a5e (How to Master Auxiliary Verbs Faster)<\/h2>\n

Reading a rules table does almost nothing on its own \u2014 I have watched students ace a grammar quiz on Monday and produce “He must to goes” on Friday. Recognition and production are different skills, and only one of them wins you IELTS points or gets you understood at work. Three habits close that gap.<\/p>\n

Write five original sentences a day, each using a different modal, about your actual life: “I should call my landlord,” “My manager might approve the budget.” Personal sentences stick because your brain has a reason to keep them. Second, read your English out loud \u2014 \u52a9\u52d5\u8a5e are usually unstressed and swallowed in fast speech (“I’ve finished” not “I have finished”), so hearing them trains your ear for how natives actually string them together. Third, when you catch a mistake, don’t just fix it \u2014 say the correct version three times. Repetition is what moves a rule from your notebook into your mouth.<\/p>\n

The video below breaks down the be-verb and auxiliary distinction with Taiwan-focused examples, which is a useful second angle if the be\/do\/have double life still feels slippery.<\/p>\n