英検準1級のensure・assure・insureの違い｜確実・安心・保険の語法【独自40問・全解説】

英検準1級でensure・assure・insureを間違える原因は、「確実にする」「人に確約する」「保険を掛ける」を日本語の「保証する」一語で暗記していることです。慶英会では英文比較12問、4択12問、語法の誤り訂正8問、オリジナル長文4篇・内容一致8問の合計40問で学習できる無料教材を公開します。全問の解答、自然な和訳、文法・語法の根拠を掲載しています。

日本英語検定協会の準1級出題形式では、短文語句空所補充は18問、長文空所補充は6問、内容一致は7問です。本記事の40問は慶英会独自の追加演習で、英検公式過去問ではありません。

まず結論｜ensure・assure・insureの意味と目的語

• ensure + 名詞 / that節：実現・安全・準備が確実になるようにする。ensure that the records are safe / ensure access。
• assure + 人 + that節：人に確信を持って説明する、安心させる。assure parents that …。
• insure + 物 / 人 + against + 危険：保険を掛け、金銭的損失に備える。insure a vehicle against theft。
• 意味の重複に注意：assure safetyのような「確実にする」の用法や、米国英語でinsureをensureと重ねる用法も存在する。以下はもっとも混同しにくい代表的語法を扱う。
• 重要な論理：「安全だと説明した」ことは「安全が検証済み」の意味ではない。「保険がある」ことは「事故が起こらない」ことでもない。

演習A｜英文比較と和訳12問

誰が説明したのか、何を確保するのか、何を保険で補償するのかを特定して訳してください。

1. A1. The principal assured parents that classes would continue.
2. A2. The principal took steps to ensure that all students could access the materials.
3. A3. The charity insured its delivery van against theft.
4. A4. The company assured customers that their data would not be sold.
5. A5. Engineers checked the doors to ensure safe access.
6. A6. The museum insured the painting for a substantial amount.
7. A7. The organizer assured us that the timetable had been revised.
8. A8. The organizer revised the schedule to ensure enough time for questions.
9. A9. The family insured its house against storm damage.
10. A10. The spokesperson assured reporters that the figures were preliminary.
11. A11. The school designed a checklist to ensure consistent grading.
12. A12. The event organizers insured expensive equipment against accidental damage.

演習B｜語法・文脈の4択12問

13. B1. The school ___ parents that the final timetable would be published on Friday. (A) insured (B) assured (C) ensured (D) ensuring
14. B2. Technicians installed extra railings to ___ safer access to the entrance. (A) ensure (B) insure (C) reassure (D) assure people
15. B3. The owner decided to ___ the building against fire damage. (A) reassure (B) ensure (C) insure (D) confirm
16. B4. The director ___ staff that no immediate closure was planned. (A) insured (B) ensured (C) ensures (D) assured
17. B5. The city collected feedback to ___ that the instructions were understandable. (A) ensure (B) insured (C) reassured (D) assured residents
18. B6. The policy did not ___ that every resident would benefit equally. (A) insure property (B) ensure (C) reassure people (D) assured
19. B7. An insurance company agreed to ___ the vehicles for the next year. (A) ensure (B) assure someone (C) insure (D) notify
20. B8. The researcher ___ colleagues that the original data would be preserved. (A) ensured (B) insured (C) guarantees (D) assured
21. B9. The committee introduced a review procedure to ___ fair treatment of applications. (A) ensure (B) insure (C) reassure (D) assured
22. B10. The company chose to ___ its research equipment against theft. (A) ensure (B) insure (C) reassure (D) verify
23. B11. Officials ___ residents that the notice contained no personal information. (A) insured (B) ensured (C) assured (D) confirming
24. B12. Careful scheduling can help ___ adequate staffing, but cannot remove every delay. (A) insure (B) reassure people (C) assure someone (D) ensure

演習C｜語法の誤り・曖昧な意味を直す8問

25. C1. The museum insured visitors that the event would proceed.
26. C2. The museum ensured the painting against theft.
27. C3. We assured that the records would be kept securely.（記録の安全な保管を確実にした、という意味）
28. C4. The charity insured enough volunteers for the event.（必要な人数を確保した、という意味）
29. C5. The teacher ensured the parents that the schedule had changed.（保護者へ説明した、という意味）
30. C6. The school assured the laboratory equipment against loss.
31. C7. The company assured that every application would be processed fairly.（応募者へ確約した、という意味）
32. C8. The insurer ensured the boat against accidental damage.

演習D｜オリジナル長文4篇・内容一致8問

長文1｜博物館の保存計画

A fictional museum planned to move fragile objects to a new storage room. Its director assured donors that the collection would remain available for research. Staff installed monitoring equipment to ensure that humidity could be controlled. The museum insured valuable objects against theft, although insurance would not prevent physical damage. Managers planned to review conditions after the move rather than assuming the new equipment offered perfect protection.

33. D1. Which action concerned insurance against financial loss? (A) Reassuring donors (B) Insuring objects against theft (C) Monitoring humidity (D) Reviewing storage conditions
34. D2. What did the museum NOT assume? (A) Some objects were fragile (B) Research access mattered (C) Monitoring equipment guaranteed perfect protection (D) Humidity should be controlled

長文2｜学校の交通支援

A school administrator assured families that a temporary bus would be tested before its route was finalized. Staff checked ramps and seating arrangements to ensure safe boarding. The contractor insured its buses against specified kinds of damage, but could not promise that traffic delays would disappear. The school collected feedback from passengers and drivers, postponing its final decision until results could be compared.

35. D3. What did staff check to support safe boarding? (A) Ramps and seating (B) Museum insurance (C) School tuition (D) Library computers
36. D4. What is correct about the contractor? (A) It eliminated all delays (B) It guaranteed every route (C) It canceled the bus trial (D) It insured buses but could not guarantee no delays

長文3｜市役所の緊急案内

A town hall revised an emergency notice after several residents misunderstood the original instructions. Officials assured the public that the new notice would be available in print and online. They trained reception staff to ensure that visitors could obtain help when needed. The building was insured against fire damage. The council emphasized, however, that insurance could not replace safety inspections or clear communication.

37. D5. What did the officials assure people of? (A) Guaranteed absence of fires (B) No need for staff (C) Availability of notices in two formats (D) Closure of the town hall
38. D6. What did the council stress? (A) Insurance replaces every inspection (B) Insurance is not a substitute for safety measures (C) All residents understood the old notice (D) Staff training was unnecessary

長文4｜研究機関とデータ検証

A researcher assured a funding committee that the team would publish its methods. To ensure accurate record keeping, a second review of data entries was introduced. The university insured expensive devices during transport to another laboratory. The committee stressed that these actions did not guarantee every future finding would be correct. Independent verification remained necessary.

39. D7. Why were devices insured? (A) To cover transport-related risks (B) To prove every finding correct (C) To eliminate reviews (D) To reassure people verbally
40. D8. What remained necessary? (A) Ending publication (B) Canceling all research (C) Replacing all researchers (D) Independent verification

全40問の模範解答・日本語訳・解説

A｜英文比較12問

1. A1：校長は授業が続くと保護者に伝えて安心させた。assure＋人＋that節。
2. A2：校長は全生徒が教材を利用できるよう対策を取った。ensure＋that節。
3. A3：慈善団体は配送車に盗難保険を掛けた。insure＋対象＋against＋危険。
4. A4：会社は顧客のデータを販売しないと約束した。assure customers。
5. A5：技術者は安全な出入りを確保するため扉を点検した。ensure safe access。
6. A6：博物館は絵画に多額の保険を掛けた。insure＋対象＋for＋補償額。
7. A7：主催者は予定表が修正済みだと私たちに確約した。assure us。
8. A8：質問時間を十分確保するため主催者が予定を修正した。ensure enough time。
9. A9：家族は嵐による損傷に備え家を保険に入れた。insure against storm damage。
10. A10：広報担当者は数値が暫定的だと記者に明言した。assure reporters。preliminaryの限定を維持。
11. A11：学校は一貫した採点を確保するため確認表を設計した。ensure consistent grading。
12. A12：主催者は高価な機材へ偶発的損傷の保険を掛けた。保険は物理的破損自体の防止とは違う。

B｜文脈4択12問

13. B1 正解B・assured：parentsという人にthat節の内容を伝えた。
14. B2 正解A・ensure：手すりで安全な出入りを確保する。
15. B3 正解C・insure：建物＋against fire damageは保険。
16. B4 正解D・assured：staffへ閉鎖予定について説明した。
17. B5 正解A・ensure：ensure that＋完全な節。
18. B6 正解B・ensure：did not ensure thatで全員への利益を保証しない。
19. B7 正解C・insure：保険会社が車両の補償を引き受ける。
20. B8 正解D・assured：assure colleagues thatで人へ確信を伝える。
21. B9 正解A・ensure：公平な審査を確保する目的。
22. B10 正解B・insure：research equipment＋against theftは保険契約。
23. B11 正解C・assured：assure residents thatで相手へ説明。
24. B12 正解D・ensure：人員確保の意味。遅延が全部消えるとは書かない。

C｜訂正8問

25. C1：The museum assured visitors that the event would proceed. 人へ説明する意味。
26. C2：The museum insured the painting against theft. 盗難への保険。
27. C3：We ensured that the records would be kept securely. 実現の確保が意図される。
28. C4：The charity ensured that enough volunteers were available for the event. 保障ではなく人数確保。
29. C5：The teacher assured the parents that the schedule had changed. parentsへ説明。
30. C6：The school insured the laboratory equipment against loss. 損失への保険。
31. C7：The company assured applicants that every application would be processed fairly. 相手を明示する。ensure thatなら公正な処理を実現する意味に変わる。
32. C8：The insurer insured the boat against accidental damage. 保険会社による補償。

D｜独自長文4篇・8問

33. D1 正解B：insured valuable objects against theft。保険の目的。
34. D2 正解C：rather than assuming … perfect protection。対策と完全な結果を分ける。
35. D3 正解A：checked ramps and seating arrangements。安全確保の実施内容。
36. D4 正解D：insured its buses … could not promise … delays。損害補償と遅延防止は別。
37. D5 正解C：available in print and online。説明した内容は二形式での通知提供。
38. D6 正解B：insurance could not replace safety inspections。保険と安全対策を区別。
39. D7 正解A：insured expensive devices during transport。運搬中の損失に備えた。
40. D8 正解D：Independent verification remained necessary。取組後も独立検証が必要。

7日間の復習手順

1. 1日目：A12文を和訳し、説明・確保・保険に分類
2. 2日目：B12問の文脈4択を解く
3. 3日目：C8問を主語と目的語に注意して訂正
4. 4日目：Dの長文4篇8問を初見で解く
5. 5日目：ensure＋名詞／that節で自作文4文
6. 6日目：assure＋人＋that節、insure＋対象＋againstで自作文4文
7. 7日目：英検協会の短文語句空所補充の公式過去問で実戦確認

よくある質問

insureとensureは絶対に交換できませんか？

米国英語ではinsureが「確実にする」にも使われます。文章の意図をはっきりさせるには、保険契約にinsure、事態の確保にensureを使い分けると理解されやすくなります。

assureは人以外を目的語に取れませんか？

assure safetyなど「確実にする」という用法もあるため絶対的な禁止ではありません。ただし「人へ説明する」意味ならassure someone that …が分かりやすい構文です。

保険を掛ければ事故を防げますか？

いいえ。insureは主として損失への金銭的な備えです。事故・盗難が起こらないこととは異なります。

独自40問の正答率から英検CSEを計算できますか？

できません。慶英会が作成した語法教材で、公式の設問数・難度・採点方式には対応していません。

関連する慶英会無料教材・学習相談

短文語句空所補充18問×2セット／英文要約の名詞化・動詞化32問／準1級文法8分野40問。

慶英会では英検準1級の語彙・語法を、長文・英文要約・意見英作文までつなげて個別指導します。最大1か月完全無料体験・学習相談はこちら。

参考にした公式・語法情報

日本英語検定協会｜準1級試験内容／BBC Learning English｜assure・ensure・insure／Microsoft Writing Style Guide｜3語の使い分け。確認日：2026年10月28日。本文・問題・解説は慶英会独自制作です。