{"id":273540,"date":"2026-09-24T03:00:28","date_gmt":"2026-09-24T08:00:28","guid":{"rendered":"https:\/\/langcom.org\/?p=273540"},"modified":"2026-09-24T03:00:28","modified_gmt":"2026-09-24T08:00:28","slug":"modal-verb-must-mustnt-a1-a1","status":"publish","type":"post","link":"https:\/\/langcom.org\/ja\/blog\/modal-verb-must-mustnt-a1-a1\/","title":{"rendered":"Learn Must and Mustn&#8217;t: Expressing Rules and Importance (A1 English Grammar)"},"content":{"rendered":"<div class=\"lc-answer\"><strong>\u5f53\u793e\u3067\u306f <span data-no-translation>must<\/span> to talk about things that are very important or necessary to do.<\/strong> It&#8217;s like saying &#8216;you have to do this&#8217; or &#8216;it is a rule&#8217;. For example, <span data-no-translation>You must listen to your teacher.<\/span> This means it is a very important rule, and you have no choice. We also use <span data-no-translation>must<\/span> for strong advice or when we are sure about something. For things that are not allowed or are forbidden, we use <span data-no-translation>mustn&#8217;t<\/span> (which is short for <span data-no-translation>must not<\/span>). It means &#8216;you cannot do this&#8217; or &#8216;it is against the rules&#8217;. For instance, <span data-no-translation>You mustn&#8217;t touch the fire.<\/span> This is a rule that says touching fire is dangerous and not allowed. Remember, <span data-no-translation>must<\/span> \u305d\u3057\u3066 <span data-no-translation>mustn&#8217;t<\/span> are modal verbs. They do not change form for different subjects (like <span data-no-translation>I must<\/span>, <span data-no-translation>he must<\/span>, <span data-no-translation>they must<\/span>), and we always use the base form of the main verb after them.<\/div>\n<h2>What is &#8216;must&#8217; for?<\/h2>\n<p>\u5f53\u793e\u3067\u306f <span data-no-translation>must<\/span> to talk about things that are very important. It shows a strong obligation or a rule.<\/p>\n<ul>\n<li><strong>Obligation or Necessity:<\/strong> When something is necessary to do. For example, <span data-no-translation>Students must wear a uniform.<\/span><\/li>\n<li><strong>Strong Advice:<\/strong> When you think something is a very good idea. For example, <span data-no-translation>You must visit the museum; it&#8217;s amazing!<\/span><\/li>\n<\/ul>\n<div class=\"lc-cta lc-cta-blended\" style=\"border-radius:14px;padding:30px;margin:30px 0;text-align:center;color:#fff;background:linear-gradient(135deg,#0E63C4,#0A2540);\"><h3 style=\"color:#fff;font-size:22px;font-weight:800;margin:0 0 8px;\">\ud83c\udf93 \u30d6\u30ec\u30f3\u30c7\u30c3\u30c9\u5b66\u7fd2\u6cd5\u3067\u82f1\u8a9e\u3092\u5b66\u307c\u3046<\/h3><p style=\"margin:0 0 10px;opacity:.95;\">\u5c11\u4eba\u6570\u5236\u30fb24\u6642\u9593365\u65e5\u5bfe\u5fdc\u306eAI\u30c1\u30e5\u30fc\u30bf\u30fc\u30fb\u30b1\u30f3\u30d6\u30ea\u30c3\u30b8\u8a66\u9a13\u5bfe\u7b56<\/p><p style=\"margin:0 0 16px;font-size:18px;\">\u4ee5\u4e0b\u306e\u30d7\u30e9\u30f3\u304b\u3089 <strong><span class=\"woocommerce-Price-amount amount\"><bdi><span class=\"woocommerce-Price-currencySymbol\" translate=\"no\" dir=\"auto\">$<\/span>39<\/bdi><\/span><\/strong> <s style=\"opacity:.6;\"><span class=\"woocommerce-Price-amount amount\"><bdi><span class=\"woocommerce-Price-currencySymbol\" translate=\"no\" dir=\"auto\">$<\/span>79<\/bdi><\/span><\/s> \u6708\u984d<\/p><a href=\"\/ja\/\" style=\"display:inline-block;margin-top:8px;padding:13px 30px;border-radius:8px;font-weight:700;text-decoration:none;background:#fff;color:#0E63C4;\">\u30af\u30e9\u30b9\u306e\u4e88\u7d04\u3092\u3059\u308b<\/a><\/div>\n<h2>What is 'mustn't' for?<\/h2>\n<p>\u5f53\u793e\u3067\u306f <span data-no-translation>mustn't<\/span> \uff08\u307e\u305f\u306f <span data-no-translation>must not<\/span>) to talk about things that are not allowed. It shows a prohibition.<\/p>\n<ul>\n<li><strong>Prohibition:<\/strong> When something is forbidden or against the rules. For example, <span data-no-translation>You mustn't take photos in the museum.<\/span><\/li>\n<li><strong>Danger:<\/strong> When something is dangerous to do. For example, <span data-no-translation>Children mustn't play with knives.<\/span><\/li>\n<\/ul>\n<h2>How do we form sentences with 'must' and 'mustn't'?<\/h2>\n<p><span data-no-translation>Must<\/span> \u305d\u3057\u3066 <span data-no-translation>mustn't<\/span> are easy to use! They are modal verbs, so they follow simple rules.<\/p>\n<ul>\n<li><strong>Always use the base form of the verb:<\/strong> After <span data-no-translation>must<\/span> \u307e\u305f\u306f <span data-no-translation>mustn't<\/span>, the next verb is always in its basic form (e.g., <span data-no-translation>go<\/span>, <span data-no-translation>eat<\/span>, <span data-no-translation>study<\/span>).<\/li>\n<li><strong>No 'to':<\/strong> \u5f53\u793e\u306f\u4ee5\u4e0b\u3092\u4f7f\u7528\u3057\u3066\u304a\u308a\u307e\u305b\u3093 <span data-no-translation>to<\/span> \u305d\u306e\u5f8c <span data-no-translation>must<\/span> \u307e\u305f\u306f <span data-no-translation>mustn't<\/span>.<\/li>\n<li><strong>No '-s' for 'he\/she\/it':<\/strong> <span data-no-translation>Must<\/span> never changes its form, even for <span data-no-translation>he<\/span>, <span data-no-translation>she<\/span>, \u3001\u307e\u305f\u306f <span data-no-translation>it<\/span>.<\/li>\n<\/ul>\n<table>\n<caption>Forms of &lt;span data-no-translation&gt;Must&lt;\/span&gt; \u305d\u3057\u3066 &lt;span data-no-translation&gt;Mustn&#039;t&lt;\/span&gt;<\/caption>\n<thead>\n<tr>\n<th>Subject<\/th>\n<th>Positive Form<\/th>\n<th>Negative Form<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><span data-no-translation>I \/ You \/ We \/ They<\/span><\/td>\n<td><span data-no-translation>must go<\/span><\/td>\n<td><span data-no-translation>mustn't go<\/span><\/td>\n<\/tr>\n<tr>\n<td><span data-no-translation>He \/ She \/ It<\/span><\/td>\n<td><span data-no-translation>must go<\/span><\/td>\n<td><span data-no-translation>mustn't go<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>\u4f8b<\/h2>\n<ul>\n<li><span data-no-translation>I must finish my homework before dinner.<\/span><\/li>\n<li><span data-no-translation>You must be quiet in the library.<\/span><\/li>\n<li><span data-no-translation>He must wear a helmet when he rides his bike.<\/span><\/li>\n<li><span data-no-translation>We mustn't talk during the exam.<\/span><\/li>\n<li><span data-no-translation>She mustn't forget her passport for the trip.<\/span><\/li>\n<li><span data-no-translation>They must arrive on time for the meeting.<\/span><\/li>\n<\/ul>\n<h2>\u7df4\u7fd2<\/h2>\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-2260\" class=\"h5p-iframe\" data-content-id=\"2260\" style=\"height:1px\" src=\"about:blank\" frameborder=\"0\" scrolling=\"no\" title=\"PT04 L6 GRAMMAR must\"><\/iframe><\/div>\n<div class=\"lc-cta lc-cta-whatsapp\" style=\"border-radius:14px;padding:30px;margin:30px 0;text-align:center;color:#fff;background:linear-gradient(135deg,#3DB16A,#1f8a4c);\"><h3 style=\"color:#fff;font-size:22px;font-weight:800;margin:0 0 8px;\">\ud83d\udcac \u500b\u5225\u306e\u30a2\u30c9\u30d0\u30a4\u30b9\u304c\u5fc5\u8981\u3067\u3059\u304b\uff1f<\/h3><p style=\"margin:0 0 16px;opacity:.95;\">\u5f53\u6821\u306f\u30b1\u30f3\u30d6\u30ea\u30c3\u30b8\u8a66\u9a13\u306e\u516c\u8a8d\u6e96\u5099\u30bb\u30f3\u30bf\u30fc\u3068\u3057\u3066\u3001\u7686\u69d8\u306b\u6700\u9069\u306a\u30b3\u30fc\u30b9\u3084\u8cc7\u683c\u53d6\u5f97\u3078\u306e\u9053\u3092\u3054\u6848\u5185\u3044\u305f\u3057\u307e\u3059\u3002\u305c\u3072\u4eca\u3059\u3050\u30a2\u30c9\u30d0\u30a4\u30b6\u30fc\u306b\u3054\u76f8\u8ac7\u304f\u3060\u3055\u3044\u3002.<\/p><a href=\"https:\/\/wa.me\/51987070865?text=Hi%2C%20I%27m%20interested%20in%20Langcom%27s%20courses%20and%20would%20like%20some%20guidance%20choosing%20the%20right%20one.\" style=\"display:inline-block;margin-top:8px;padding:13px 30px;border-radius:8px;font-weight:700;text-decoration:none;background:#fff;color:#1f8a4c;\">WhatsApp\u3067\u30a2\u30c9\u30d0\u30a4\u30b6\u30fc\u3068\u30c1\u30e3\u30c3\u30c8<\/a><\/div>\n<h2>\u30b9\u30da\u30a4\u30f3\u8a9e\u8a71\u8005\u304c\u3088\u304f\u72af\u3059\u9593\u9055\u3044<\/h2>\n<p>Many Spanish speakers make small mistakes with <span data-no-translation>must<\/span> \u305d\u3057\u3066 <span data-no-translation>mustn't<\/span>. Here are the most common ones to avoid:<\/p>\n<ul>\n<li><strong>Using 'to' after <span data-no-translation>must<\/span> \u307e\u305f\u306f <span data-no-translation>mustn't<\/span>:<\/strong>\n<ul>\n<li>\u274c <span data-no-translation>You must to study.<\/span><\/li>\n<li>\u2705 <span data-no-translation>You must study.<\/span><\/li>\n<\/ul>\n<\/li>\n<li><strong>Adding '-s' to <span data-no-translation>must<\/span> for 'he', 'she', 'it':<\/strong>\n<ul>\n<li>\u274c <span data-no-translation>He musts go.<\/span><\/li>\n<li>\u2705 <span data-no-translation>He must go.<\/span><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>\u3088\u304f\u3042\u308b\u8cea\u554f<\/h2>\n<h3>What is the main use of 'must'?<\/h3>\n<p><span data-no-translation>Must<\/span> is for strong rules, obligations, or things that are very important to do. For example, <span data-no-translation>You must listen to your parents.<\/span><\/p>\n<h3>What is the main use of 'mustn't'?<\/h3>\n<p><span data-no-translation>Mustn't<\/span> is for things that are not allowed or forbidden. For example, <span data-no-translation>You mustn't run in the corridors.<\/span><\/p>\n<h3>Can I say 'must not' instead of 'mustn't'?<\/h3>\n<p>\u306f\u3044\u3001, <span data-no-translation>must not<\/span> is the full form, and <span data-no-translation>mustn't<\/span> is the short, common form. They mean the same thing.<\/p>\n<h3>Does 'must' change for 'he\/she\/it'?<\/h3>\n<p>No, <span data-no-translation>must<\/span> never changes its form. It is always <span data-no-translation>must<\/span> for all subjects (I, you, he, she, it, we, they).<\/p>\n<h2>\u95a2\u9023\u30ec\u30c3\u30b9\u30f3<\/h2>\n<ul>\n<li><a href=\"https:\/\/langcom.org\/ja\/?p=272776\">Modal verbs<\/a><\/li>\n<li><a href=\"https:\/\/langcom.org\/ja\/?p=273037\">Modal verbs<\/a><\/li>\n<li><a href=\"https:\/\/langcom.org\/ja\/?p=273133\">Modal verbs<\/a><\/li>\n<li><a href=\"https:\/\/langcom.org\/ja\/?p=273153\">Modal verbs<\/a><\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p>We use must to talk about things that are very important or necessary to do. It&#8217;s like saying &#8216;you have to do this&#8217; or &#8216;it is a rule&#8217;. For example, You must listen to your teacher. This means it is a very important rule, and you have no choice. We also use must for strong advice or when we are sure about something. For things that are not allowed or are forbidden, we use mustn&#8217;t (which is short for must not). It means &#8216;you cannot do this&#8217; or &#8216;it is against the rules&#8217;. For instance, You mustn&#8217;t touch the fire. This is a rule that says touching fire is dangerous [&hellip;]<\/p>\n","protected":false},"author":192,"featured_media":274756,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"bwfblock_default_font":"","langcom_teaches":"Modal verbs","langcom_cefr":"A1","langcom_type":"grammar","langcom_faq":"[{\"q\": \"What is the main use of 'must'?\", \"a\": \"<span data-no-translation>Must<\/span> is for strong rules, obligations, or things that are very important to do. For example, <span data-no-translation>You must listen to your parents.<\/span>\"}, {\"q\": \"What is the main use of 'mustn't'?\", \"a\": \"<span data-no-translation>Mustn't<\/span> is for things that are not allowed or forbidden. For example, <span data-no-translation>You mustn't run in the corridors.<\/span>\"}, {\"q\": \"Can I say 'must not' instead of 'mustn't'?\", \"a\": \"Yes, <span data-no-translation>must not<\/span> is the full form, and <span data-no-translation>mustn't<\/span> is the short, common form. They mean the same thing.\"}, {\"q\": \"Does 'must' change for 'he\/she\/it'?\", \"a\": \"No, <span data-no-translation>must<\/span> never changes its form. It is always <span data-no-translation>must<\/span> for all subjects (I, you, he, she, it, we, they).\"}]","_kiss_seo_title":"","_kiss_seo_excerpt":"We use must to talk about things that are very important or necessary to do. It's like saying 'you have to do this' or 'it is a rule'.","_mwseo_canonical":"","_mwseo_keywords":"","_mwseo_primary_category":0,"footnotes":""},"categories":[608],"tags":[651,1228],"formats":[],"class_list":["post-273540","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-a1-beginner-english-for-kids","tag-grammar","tag-must"],"dsm_author":{"name":"\u30e9\u30a6\u30eb","avatar_url":"https:\/\/langcom.org\/wp-content\/uploads\/nsl_avatars\/1de86ea706740d324aaef3dd8bf0843b.png","archive_link":"https:\/\/langcom.org\/ja\/blog\/author\/raulmaguinahamann\/","biodata":""},"dsm_categories":[{"term_name":"A1 Beginner English for Kids","term_id":608,"term_link":"https:\/\/langcom.org\/ja\/blog\/category\/learn-english\/english-for-kids\/a1-beginner-english-for-kids\/"}],"dsm_attachment_categories":[],"dsm_featured_image":{"thumbnail":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-150x150.webp","medium":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-300x158.webp","medium_large":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-768x403.webp","large":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-1024x538.webp","1536x1536":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1.webp","2048x2048":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1.webp","trp-custom-language-flag":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-18x9.webp","et-pb-post-main-image":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-400x250.webp","et-pb-post-main-image-fullwidth":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-1080x630.webp","et-pb-portfolio-image":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-400x284.webp","et-pb-portfolio-module-image":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-510x382.webp","et-pb-portfolio-image-single":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-1080x567.webp","et-pb-gallery-module-image-portrait":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-400x516.webp","et-pb-post-main-image-fullwidth-large":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1.webp","et-pb-image--responsive--desktop":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1.webp","et-pb-image--responsive--tablet":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-980x515.webp","et-pb-image--responsive--phone":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-480x252.webp","woocommerce_thumbnail":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-300x300.webp","woocommerce_single":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-600x315.webp","woocommerce_gallery_thumbnail":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1-100x100.webp","full":"https:\/\/langcom.org\/wp-content\/uploads\/2026\/07\/modal-verbs-a1-grammar-english-langcom-1.webp"},"dsm_comment_count":0,"_links":{"self":[{"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/posts\/273540","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/users\/192"}],"replies":[{"embeddable":true,"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/comments?post=273540"}],"version-history":[{"count":0,"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/posts\/273540\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/media\/274756"}],"wp:attachment":[{"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/media?parent=273540"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/categories?post=273540"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/tags?post=273540"},{"taxonomy":"post_format","embeddable":true,"href":"https:\/\/langcom.org\/ja\/wp-json\/wp\/v2\/formats?post=273540"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}