impurity
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C1 noun /ɪmˈpjʊərəti/

impurity

不純物
Meaning
the state of being unclean or contaminated; a substance that makes something impure
Example
The scientist removed every impurity from the water sample.
科学者は水のサンプルからすべての不純物を取り除いた。
C1 adjective ˌɪn.təˈmɪt.ənt

intermittent

断続的
Meaning
Happening irregularly, not continuously.
Example
The rain was intermittent throughout the day.
雨は一日中断続的でした。
C1 adjective /ɪˈnɔːrdənət/

inordinate

過度の
Meaning
Excessive or unusually large in degree.
Example
She spent an inordinate amount of time on her phone.
彼女は電話に過度の時間を費やしました。
C1 verb ɪˈmɜːrs

immerse

浸る
Meaning
To involve oneself deeply in a particular activity or interest; to surround completely.
Example
Immerse yourself in the new language.
新しい言語に浸ってください。
C1 noun /aɪl/

isle

小さな島
Meaning
A small island or peninsula, often poetic or literary.
Example
They spent their honeymoon on a beautiful tropical isle.
彼らは美しい熱帯の島でハネムーンを過ごしました。
C1 noun /ˈɪnlɛt/

inlet

入り江
Meaning
A small arm of the sea, a lake, or a river; an opening or passage for entry.
Example
The boat entered a narrow inlet along the coast.
船は海岸沿いの狭い入り江に入った。
C1 adjective /ɪˈnuːmərəbəl/

Innumerable

無数; 数えきれない; 無限
Meaning
too many to be counted; countless; infinite in number
Example
There are innumerable stars in the night sky that we cannot see with our naked eyes.
夜空には数えきれない星があり、私たちは裸眼では見ることができません。
C1 adjective /ˌɪntəˈrɑːɡətɪv/

interrogative

疑問の
Meaning
Relating to or conveying a question; in grammar, used to form questions.
Example
She raised an interrogative eyebrow when she heard the news.
彼女はそのニュースを聞いて疑問のまなざしを向けました。
C1 adjective ɪmˈpɛkəbl

impeccable

完璧な
Meaning
In accordance with the highest standards; faultless.
Example
His impeccable taste in fashion was admired by all his peers.
彼の完璧なファッションセンスは、すべての同僚に賞賛されました。
C1 noun /ˈɪn.fən.tri/

Infantry

歩兵
Meaning
soldiers marching or fighting on foot; foot soldiers collectively
Example
The infantry advanced across the battlefield on foot.
歩兵は戦場を徒歩で進んだ。
C1 adjective ɪnˈsaɪ.sɪv

incisive

鋭い
Meaning
Intelligently analytical and clear-thinking; showing clear thought and good understanding of what is important.
Example
His incisive comments revealed the core issues.
彼の鋭いコメントは核心的な問題を明らかにしました。
C1 noun /ɪˌreɡjəˈlærɪti/

irregularity

不規則性
Meaning
lack of regularity or consistency; a deviation from what is normal, expected, or orderly
Example
The audit revealed several financial irregularities in the company’s records.
監査により、その会社の記録にいくつかの財務上の不規則性が明らかになった。
C1 noun/verb /ˈɪmprɪnt/

imprint

刻印
Meaning
A mark or impression made by pressure; to establish or fix firmly in someone's mind.
Example
The event left an indelible imprint on the city's history.
その出来事は都市の歴史に消えない刻印を残した。
C1 noun /ɪnˈækjʊrəsi/

inaccuracy

不正確さ
Meaning
lack of accuracy or precision; an incorrect or wrong detail
Example
The report contained several factual inaccuracies.
その報告書にはいくつかの不正確さがあった。
C1 noun /ɪnˈfɜːməri/

infirmary

診療所
Meaning
A hospital or place where the sick or injured are cared for.
Example
The school had an infirmary for minor injuries.
学校には軽傷のための診療所がありました。
C1 adjective /ɪnˈseɪʃəbl̩/

insatiable

満たされない
Meaning
impossible to satisfy; always wanting more
Example
Her insatiable curiosity drove her to read every book in the library.
彼女の満たされない好奇心は、図書館のすべての本を読むように彼女を駆り立てた。
C1 noun /ɪˈmiːdiəsi/

immediacy

即時性, 緊迫感
Meaning
The quality of bringing one into direct and instant involvement with something, giving rise to a sense of urgency or excitement.
Example
The immediacy of digital communication has reshaped business operations.
デジタルコミュニケーションの即時性は、ビジネスの運営方法を変えました。
C1 adjective /ˈɪnərmoʊst/

Innermost

最も深い; 最も個人的な
Meaning
most private and secret; deepest; most personal
Example
She shared her innermost feelings with her closest friend.
彼女は最も深い感情を最も親しい友人と共有しました。
C1 verb /ɪnˈvɪɡ.ər.eɪt/

invigorate

活性化する
Meaning
To give strength or energy to someone or something.
Example
A morning walk can invigorate both body and mind.
朝の散歩は、体と心を活性化することができます。
C1 adjective /ɪnˈvɑːlənˌtɛri/

involuntary

不随意
Meaning
done without will or conscious control
Example
He gave an involuntary shiver when he heard the loud noise.
彼は大きな音を聞いたとき、不随意に震えた。
C1 noun ˈɪm.pɪ.təs

impetus

推進力
Meaning
The force or motivation that drives something forward; momentum.
Example
The new policy provided an impetus for economic growth.
新しい政策は経済成長のための推進力を提供しました。
C1 adjective /ɪnˈdɪɡnənt/

indignant

憤慨した
Meaning
Feeling or showing anger at something considered unfair or unjust.
Example
She was indignant when accused of cheating.
彼女は不正行為を非難されたとき、憤慨していた。
C1 adjective /ˌɪn.səbˈstæn.ʃəl/

insubstantial

不十分な
Meaning
Lacking strength, substance, or solidity.
Example
The evidence provided was insubstantial and unconvincing.
提供された証拠は不十分で説得力がなかった。
C1 noun /ɪnˈfjuːʒən/

infusion

注入
Meaning
the act of introducing something into another; a drink made by steeping leaves or herbs in liquid
Example
She prepared a calming infusion of chamomile tea.
彼女はカモミールティーの落ち着く注入を準備しました。
C1 adjective /ɪˈrɛvərənt/

irreverent

不敬な
Meaning
showing a lack of respect for people or things that are usually respected
Example
The comedian’s irreverent jokes offended some of the audience.
コメディアンの不敬なジョークは、観客の一部を不快にさせた。
C1 verb /ɪˈnɔːɡjʊreɪt/

inaugurate

Meaning
To formally begin or introduce something, especially with a ceremony.
Example
The mayor will inaugurate the new bridge tomorrow.
C1 adjective, noun /ˈɪnvəlɪd/ (adjective), /ɪnˈvælɪd/ (noun)

invalid

無効
Meaning
Not valid; having no force or effect. Also refers to a person too weak or ill to care for themselves.
Example
The court declared the contract invalid.
裁判所は契約を無効と宣言した。
C1 noun /ˌɪntɪˈmeɪʃən/

intimation

示唆
Meaning
A subtle or indirect hint or suggestion.
Example
She gave no intimation of her plans.
彼女は自分の計画について何の示唆も与えなかった。
C1 noun /ɪmˈpɛdɪmənt/

impediments

障害
Meaning
A hindrance or obstruction in doing something; things that prevent progress or achievement.
Example
Economic impediments often hinder social development.
経済的な障害はしばしば社会的発展を妨げる。
C1 verb /ɪnˈtɪmɪdeɪt/

intimidate

Meaning
To frighten or overawe someone, especially to make them do what one wants.
Example
The bully tried to intimidate the smaller kids.
C1 adjective /ɪnˈæk.tɪv/

Inactive

非アクティブ
Meaning
not active; not working; dormant; idle
Example
The volcano has been inactive for over a century.
この火山は1世紀以上も活動していない。
C1 noun /ɪnˈdjuːsmənt/

inducement

誘因
Meaning
something that persuades or encourages someone to do something
Example
The company offered a bonus as an inducement to employees.
会社は従業員にインセンティブとしてボーナスを提供しました。
C1 adjective /ɪˈmeʒərəbəl/

Immeasurable

計り知れない
Meaning
too large or extensive to measure; boundless
Example
The immeasurable love of a mother knows no bounds.
母の計り知れない愛には限界がない。
C1 noun /ˈɪŋ.krə.mənt/

Increment

増加
Meaning
an increase or addition, especially one of a series on a fixed scale; a regular increase in salary
Example
He received an annual increment of five percent in his salary this year.
彼は今年、自分の給料に5パーセントの年次増加を受け取った。
C1 noun /ˈɪn.floʊ/

inflow

流入
Meaning
The movement of things such as money, people, or water into a place.
Example
The inflow of tourists boosted the local economy.
観光客の流入が地域経済を活性化させた。
C1 adjective /ɪnˈkrɛdjələs/

incredulous

Meaning
unwilling or unable to believe something
Example
He gave her an incredulous look when she claimed she could fly.
C1 adjective /ɪmˈprɒmp.tjuː/

impromptu

即興
Meaning
Done without being planned, organized, or rehearsed; spontaneous.
Example
He gave an impromptu speech at the event.
彼はイベントで即興のスピーチを行いました。
C1 noun /ɪmˈbæl.əns/

Imbalance

不均衡
Meaning
lack of proportion or relation between corresponding things; unequal distribution
Example
The doctor said the patient's dizziness was caused by an inner ear imbalance.
医者は患者のめまいが内耳の不均衡によって引き起こされたと言いました。
C1 adjective ɪnˈtrɪn.zɪk

intrinsic

内在的, 本質的, 自然な
Meaning
Belonging naturally; essential. Existing as a natural or basic part of something.
Example
Creativity is an intrinsic quality of a great artist.
創造性は偉大なアーティストの内在的な資質です。
C1 noun /ˌɪnkəmˌpætəˈbɪlɪti/

incompatibility

非互換性
Meaning
the state of being unable to exist or work together harmoniously; lack of compatibility
Example
The project failed because of incompatibility between the two software systems.
2つのソフトウェアシステムの非互換性のため、そのプロジェクトは失敗した。
C1 verb ɪˈnɪʃɪeɪtɪd

initiated

開始された
Meaning
Caused a process or action to begin; started something.
Example
The project was initiated to enhance marine biodiversity.
プロジェクトは海洋生物多様性を向上させるために開始されました。
C1 noun /ˈɪnˌmeɪt/

inmate

囚人
Meaning
a person confined to an institution such as a prison or hospital
Example
The prison has over a thousand inmates.
刑務所には千人以上の囚人がいます。
C1 adjective /ˌɪndɪˈfɛnsəbl̩/

indefensible

弁護できない
Meaning
not able to be protected or justified
Example
The minister’s remarks were considered indefensible by the public.
大臣の発言は公衆によって弁護できないとみなされました。
C1 adjective /ɪnˈfæləbl̩/

infallible

間違いない
Meaning
incapable of making mistakes or being wrong
Example
Her judgment seemed infallible in matters of finance.
彼女の判断は財務問題において間違いないように見えた。
C1 noun ɪnˈsɛpʃən

inception

始まり
Meaning
The establishment or starting point of an institution or activity.
Example
The inception of the company marked a new era in the industry.
その企業のインセプションは業界に新しい時代を築きました。
C1 verb /ˌɪntərˈsɛpt/

intercept

Meaning
to stop, catch, or seize something on its way from one place to another
Example
The police intercepted the stolen car before it crossed the border.
C1 adjective /ɪnˈsɛnsəbl/

insensible

無意識
Meaning
Unconscious; unaware of or indifferent to something.
Example
He was insensible to the cold as he lay in the snow.
彼は雪の中で横たわっているとき、寒さに無意識でした。
C1 noun /ˌɪntərˈmiːdiˌɛri/

intermediary

仲介者
Meaning
A person who acts as a link between people in order to try to bring about an agreement; a mediator.
Example
The diplomat served as an intermediary between the two conflicting nations.
外交官は二つの対立する国々の間で仲介者として機能した。
C1 adjective /ˌɪrɪˈspɛktɪv/

Irrespective

無視して; 問わず
Meaning
without taking something into account; regardless of
Example
All students will be treated equally, irrespective of their background.
すべての学生は、背景に関係なく平等に扱われます。
C1 noun ɪnˌten.sɪ.fɪˈkeɪ.ʃən

intensification

強化
Meaning
The process of becoming or making something more intense or extreme.
Example
The intensification of climate change requires urgent action.
気候変動の強化は緊急の行動を必要とします。
C1 noun /ˈɪmɪdʒəri/

imagery

イメージ
Meaning
visually descriptive or figurative language, especially in a literary work
Example
The poet's use of imagery brought the scene to life.
詩人のイメージの使用は、シーンに命を吹き込みました。
C1 noun /ˌɪməˈtjʊərəti/

immaturity

未熟さ
Meaning
the state of not being fully developed emotionally, mentally, or physically; lack of maturity
Example
His immaturity made it difficult for him to handle responsibility.
彼の未熟さは責任を果たすことを難しくした。
C1 noun /ˈɪn.tə.lekt/

intellect

知能
Meaning
The ability to think, reason, and understand objectively.
Example
Her intellect is admired by all her colleagues.
彼女の知能はすべての同僚に賞賛されています。
C1 noun /ˌɪnɪkˈspɪəriəns/

inexperience

未経験
Meaning
Lack of knowledge or skill in a particular activity or field.
Example
His inexperience in handling negotiations was evident.
交渉における彼の未経験は明らかでした。
C1 noun /ˌɪnsɪɡˈnɪfɪkəns/

insignificance

重要でないこと
Meaning
The quality of being unimportant or trivial.
Example
He felt a sense of insignificance in the vast universe.
彼は広大な宇宙で重要でないことを感じました。
C1 adjective /ˌɪndɪˈsaɪsɪv/

Indecisive

優柔不断な
Meaning
unable to make decisions quickly; hesitant; wavering
Example
She was indecisive about which university to attend.
彼女はどの大学に入学すべきか決めかねていた。
C1 adjective /ɪnˈkɒŋɡruəs/

incongruous

不調和
Meaning
Not fitting in with or suitable for the surroundings.
Example
His jokes were incongruous during the serious meeting.
彼の冗談は真面目な会議では不調和だった。
C1 adjective ˌɪn.krəˈmen.təl

incremental

増分的
Meaning
Relating to or denoting an increase or addition, especially one of a series on a fixed scale; proceeding in small stages.
Example
Incremental changes ensure sustainability.
増分的な変化は持続可能性を確保します。
C1 adjective /ˌɪndɪˈspjuːtəbəl/

Indisputable

議論の余地がない; 否定できない; 確定的
Meaning
impossible to deny or argue against; undeniable; certain
Example
The evidence against him was indisputable.
彼に対する証拠は議論の余地がなかった。
C1 adjective /ɪnˈtjuː.ɪ.tɪv/

intuitive

直感的
Meaning
Based on instinctive understanding rather than reasoning.
Example
The software has an intuitive design that makes it easy to use.
そのソフトウェアは直感的なデザインを持っており、使いやすいです。
C1 verb /ɪnˈterəˌɡeɪt/

interrogate

尋問する
Meaning
to ask someone questions in a thorough and formal way; to question intensively
Example
The police interrogated the suspect for hours.
警察は容疑者を何時間も尋問した。
C1 adjective /ɪmˈpɑːrʃəl/

Impartial

公正; 中立的
Meaning
treating all sides fairly; unbiased; neutral
Example
A good judge must remain impartial throughout the trial.
優れた裁判官は裁判中に公正を保たなければなりません。
C1 adjective /ɪnˈveə.ri.ə.bəl/

Invariable

不変の; 一定の; 常に同じ
Meaning
never changing; constant; always the same
Example
His invariable routine includes morning exercise and coffee.
彼の不変のルーチンには、朝の運動とコーヒーが含まれています。
C1 verb /ɪmˈbɛd/

imbed

埋め込む
Meaning
To fix firmly or deeply in a surrounding mass.
Example
The journalist imbedded himself with the troops to report firsthand.
ジャーナリストは部隊に埋め込まれて、最前線から報告を行った。
C1 noun /ɪnˌtɪmɪˈdeɪʃən/

intimidation

威圧
Meaning
The action of frightening or threatening someone to make them do something.
Example
The workers reported cases of intimidation by the management.
労働者たちは経営陣による威圧の事例を報告しました。
C1 adjective /ɪmˈpɜːrviəs/

impervious

透過しない
Meaning
Not allowing fluid to pass through; unable to be affected by something.
Example
The jacket is impervious to rain.
ジャケットは雨に透過しません。
C1 adjective /ˈɪndɪɡoʊ bluː/

Indigo-blue

インディゴブルー
Meaning
a deep blue color with a purplish tinge
Example
The indigo-blue sky looked magnificent at twilight.
インディゴブルーの空は夕暮れ時に壮大に見えた。
C1 noun /ɪˌluːmɪˈneɪʃən/

illumination

Meaning
the act of lighting something or making something clear
Example
The street was filled with bright illumination from the lamps.
C1 adjective ˌɪn.təˈdɪs.ɪ.plɪ.nər.i

interdisciplinary

学際的
Meaning
Relating to more than one branch of knowledge.
Example
The interdisciplinary approach in education enhances problem-solving skills.
教育における学際的アプローチは、問題解決スキルを向上させる。
C1 adjective /ɪˈlʌstriəs/

illustrious

著名
Meaning
Well known, respected, and admired for past achievements.
Example
She had an illustrious career in medicine.
彼女は医学の分野で著名なキャリアを持っていた。
C1 adjective /ɪnˈhɛrənt/

inherent

固有の
Meaning
Existing in something as a natural, permanent, or essential quality.
Example
There are inherent risks in extreme sports.
エクストリームスポーツには固有のリスクが存在する。
C1 noun /ˌɪn.dɪˈsɪʒ.ən/

Indecision

優柔不断; 決断力の欠如; 迷い
Meaning
the inability to make decisions quickly; uncertainty about what to do
Example
Her indecision about which job offer to accept caused her to miss both opportunities.
どの仕事のオファーを受けるかについての優柔不断さが、両方のチャンスを逃す原因となった。
C1 adjective /ɪnˈdefɪnət/

Indefinite

不確定な
Meaning
not clearly defined; uncertain; vague; unlimited in time
Example
The meeting has been postponed for an indefinite period.
会議は不確定な期間に延期されました。
C1 adjective /ˌɪməˈtɪəriəl/

immaterial

無関係
Meaning
Not important or relevant; lacking physical substance.
Example
The judge ruled that the argument was immaterial to the case.
裁判官はその議論が事件に関係ないと判断しました。
C1 adjective /ˌɪnɔːrˈɡænɪk/

inorganic

無機の
Meaning
relating to substances that are not derived from living organisms; lacking organic structure or growth
Example
Inorganic compounds are commonly studied in chemistry labs.
無機化合物は化学の基本です。
C1 verb /ɪnˈtɒksɪkeɪt/

intoxicate

幸せ
Meaning
to make someone lose control of their faculties or behavior due to alcohol or drugs
Example
The strong drink quickly intoxicated him.
彼女は賞を受け取ったとき、自分の幸せを隠すことができなかった。
C1 adjective /ˌɪnədˈmɪsəbl̩/

inadmissible

受け入れられない
Meaning
Not allowed, especially as evidence in a court of law.
Example
The judge ruled the evidence inadmissible.
裁判官は証拠を受け入れられないと判断しました。
C1 noun /ɪˈrɛlɪvənsi/

irrelevancy

無関係性
Meaning
the state of being unrelated or unimportant to the matter at hand
Example
The judge dismissed the argument because of its irrelevancy to the case.
裁判官はその主張が事件と無関係であるとして退けた。
C1 noun /ɪnˈdɪɡ.nə.ti/

Indignity

屈辱
Meaning
treatment or circumstances that cause one to feel shame or loss of dignity; humiliation
Example
She refused to suffer the indignity of being searched without proper cause.
彼女は正当な理由もなく荷物検査を受けるという屈辱に耐えることを拒んだ。
C1 verb /ˌɪn.trəˈspekt/

introspect

内省する
Meaning
To examine one's own thoughts, feelings, or mental state.
Example
He often introspects before making important decisions.
彼は重要な決定を下す前にしばしば自己分析をします。
C1 noun /ɪnˈdʒʌŋkʃən/

injunction

差止命令
Meaning
A judicial order restraining a person from an action or compelling a certain act.
Example
The court issued an injunction to stop the company from polluting the river.
裁判所は、会社が河川を汚染するのを防ぐために差止命令を出した。
C1 adjective /ˌɪntərˈtʃeɪndʒəbl/

interchangeable

交換可能な
Meaning
able to be exchanged with each other without difference or loss of function
Example
These machine parts are interchangeable, so they can be replaced easily.
これらの機械部品は交換可能なため、簡単に交換できます。
C1 noun /ɪnˈædɪkwəsi/

inadequacy

不十分さ
Meaning
lack of sufficient ability, quality, or strength; a feeling of not being good enough
Example
She struggled with feelings of inadequacy at work despite her strong qualifications.
十分な資格があるにもかかわらず、彼女は職場で不十分さを感じていた。
C1 verb ɪˈnɔː.ɡjə.reɪ.tɪd

inaugurated

開会
Meaning
Begin or introduce (a system, policy, or period) formally.
Example
The organization was inaugurated officially.
その組織は正式に開会されました。
C1 noun ˌɪn.tuˈɪʃ.ən

intuition

直感
Meaning
The ability to understand something immediately, without the need for conscious reasoning.
Example
Her intuition told her something was wrong.
彼女の直感は何かが間違っていると言った。
C1 verb /ɪnˈfɛst/

infest

侵入する
Meaning
to overrun in large numbers, especially so as to cause damage or discomfort
Example
The old house was infested with rats.
古い家はネズミで侵されていました。
C1 verb /ˌɪnstɪˈtjuːʃənəlaɪz/

institutionalize

制度化する
Meaning
to establish something as a formal institution, custom, or practice
Example
The government seeks to institutionalize environmental protection.
政府は環境保護を制度化しようとしています。
C1 adjective /ɪnˈsɪdiəs/

insidious

陰険な
Meaning
Proceeding in a gradual, subtle way but with harmful effects.
Example
The insidious spread of misinformation can damage trust.
誤った情報の陰険な広がりは信頼を傷つける可能性がある。
C1 noun /ɪnˈsɒm.ni.ə/

Insomnia

不眠症
Meaning
habitual sleeplessness; inability to sleep; the condition of being unable to sleep
Example
Her chronic insomnia made it difficult for her to concentrate during work hours.
彼女の慢性的な不眠症は、仕事中に集中するのを難しくさせた。
C1 noun /ˌɪnˈdɪsəplɪn/

indiscipline

規律の欠如
Meaning
lack of discipline or self-control; failure to obey rules or maintain order
Example
Indiscipline among the students disrupted the learning environment.
学生の規律の欠如が学習環境を乱した。
C1 adjective /ˌɪrɪˈprɛsəbl̩/

irrepressible

抑制できない
Meaning
Impossible to control or restrain.
Example
She had an irrepressible urge to laugh during the speech.
彼女はスピーチ中に抑制できない笑いの衝動を隠すことができませんでした。
C1 adjective ɪnˈdel.ə.bəl

indelible

消えない
Meaning
Making marks that cannot be removed; impossible to forget or remove.
Example
Her speech left an indelible mark on the audience.
彼女のスピーチは聴衆に消えない印象を残しました。
C1 noun /ɪnˈhɛrɪtər/

inheritor

相続人
Meaning
a person who receives money, property, or a title when someone dies
Example
She became the inheritor of her family's estate.
彼女は家族の財産の相続人となった。
C1 adjective ɪˈluː.sər.i

illusory

幻の
Meaning
Based on illusion; not real although seeming to be.
Example
His sense of security was entirely illusory.
彼の安全感は完全に幻のものだった。
C1 adjective /ˌaɪ.di.əˈlɒdʒ.ɪ.kəl/

ideological

イデオロギー的
Meaning
Relating to or based on a system of ideas or beliefs.
Example
The two parties are divided by deep ideological differences.
二つの党は深いイデオロギー的な違いによって分裂している。
C1 adjective /ɪˈrɛvəkəbl/

irrevocable

取り消し不可能
Meaning
Not able to be revoked, changed, or undone.
Example
She made an irrevocable decision to leave the company.
彼女は会社を辞めるという取り消し不可能な決定を下した。
C1 adjective /ɪˈnɜːrt/

inert

不活性
Meaning
lacking the ability or strength to move or act; chemically inactive
Example
The patient remained inert on the bed.
患者はベッドで動かずにじっとしていました。
C1 adjective /ˌɪnsərˈmaʊntəbl/

insurmountable

克服不可能
Meaning
Too great to be overcome.
Example
The explorers faced insurmountable odds in the desert.
探検者たちは砂漠で克服不可能な障害に直面した。
C1 adjective /ɪnˈdetɪd/

Indebted

借金がある; 感謝している
Meaning
owing money or gratitude to someone; obligated; grateful
Example
I am deeply indebted to my teacher for all her guidance.
私は先生のすべての指導に深く感謝しています。
C1 adjective /ˌɪnɪkˈskjuːzəbl/

inexcusable

許しがたい
Meaning
Too bad to be justified or overlooked; unforgivable.
Example
His rude behavior was inexcusable.
彼の無礼な行動は許しがたいものでした。
C1 adverb /ˌɪnsɪˈdɛntəli/

incidentally

ちなみに
Meaning
by the way; used to introduce a remark not directly related to the main subject
Example
Incidentally, did you know that she studied in Paris?
ちなみに、彼女がパリで勉強していたことを知っていましたか？
C1 verb /ˈaɪdəlaɪz/

idolize

偶像視する
Meaning
To admire or worship someone excessively.
Example
Fans often idolize celebrities for their talent and lifestyle.
ファンはしばしばその才能とライフスタイルのために有名人を偶像視します。
C1 adjective /ɪnˈsteɪbəl/

instable

不安定な
Meaning
not stable; liable to change, collapse, or fail; lacking firmness or reliability
Example
The instable political situation worried foreign investors.
不安定な政治状況が外国の投資家を心配させた。
C1 verb /ˈɪnstɪˌɡeɪt/

instigate

扇動する
Meaning
To bring about or initiate an action, often something negative.
Example
He was accused of instigating the riot.
彼は暴動を扇動したとして告発された。
C1 verb /ɪmˈpɛrɪl/

imperil

危険にさらす
Meaning
To put in danger or at risk.
Example
Reckless driving can imperil the lives of others.
無謀な運転は他人の命を危険にさらす可能性があります。
C1 noun ˌɪrɪˈvɜːrsəbl ˈdæmɪdʒ

irreversible damage

取り返しのつかない損害
Meaning
Harm or injury that cannot be undone or repaired.
Example
Climate change causes irreversible damage to ecosystems.
気候変動は生態系に取り返しのつかない損害を与えます。
C1 noun /ˌɪn.səˌbɔːr.dɪˈneɪ.ʃən/

insubordination

反抗
Meaning
Defiance of authority; refusal to obey orders.
Example
The soldier was punished for insubordination during the mission.
その兵士はミッション中の反抗で罰せられました。
C1 noun /ˌɪndɪɡˈneɪʃən/

indignation

憤慨
Meaning
Strong displeasure or anger caused by something unjust, offensive, or insulting.
Example
Public indignation grew after the unfair verdict.
不公平な判決の後で、公衆の憤慨が高まった。
C1 adjective /ɪmˈpʌlsɪv/

impulsive

衝動的な, 直感的な
Meaning
acting suddenly without careful thought
Example
She made an impulsive decision to buy the car.
彼女は衝動的な決定で車を買うことにしました。
C1 noun /ˈɪnsɪdəns/

incidence

発生率
Meaning
the occurrence, rate, or frequency of something
Example
The incidence of road accidents has decreased this year.
今年の道路事故の発生率は減少しました。
C1 verb /ɪmˈpɛər/

impair

損なう
Meaning
to weaken or damage something, especially a function or ability
Example
Smoking can impair your lung capacity.
喫煙は肺活量を害する可能性があります。
C1 adjective /ɪˈmjuː.tə.bəl/

immutable

不変の
Meaning
Unchangeable, permanent, or fixed
Example
The laws of physics are considered immutable.
物理法則は不変と見なされます。
C1 noun /ˌɪnsəˈfɪʃənsi/

insufficiency

不足
Meaning
The state of not being enough or not being adequate.
Example
The project failed due to the insufficiency of funds.
プロジェクトは資金不足のため失敗しました。
C1 adjective ˌɪn.tə.dʒen.əˈreɪ.ʃən.əl

intergenerational

世代間、異なる世代間で発生する
Meaning
Existing or occurring between different generations of a family.
Example
Intergenerational wisdom ensures cultural continuity.
インタージェネレーショナルな知恵は文化的継続性を確保する。
C1 noun /ˌɪnækˈtɪvɪti/

inactivity

不活動
Meaning
the state of not being active physically or mentally; lack of action
Example
Prolonged inactivity can negatively affect both physical and mental health.
長期間の不活動は身体的および精神的健康に悪影響を与えます。
C1 adjective ˌɪn.təˈstel.ər

interstellar

星間の、インターステラ、宇宙の
Meaning
Occurring or situated between stars.
Example
Scientists study interstellar travel possibilities.
科学者たちはインターステラ旅行の可能性を研究しています。
C1 adjective /ˌɪnədˈvɜːrtənt/

inadvertent

意図しない, 不注意な
Meaning
Not resulting from or achieved through deliberate planning; unintentional.
Example
Her inadvertent mistake caused a delay in the project.
彼女の不注意なミスがプロジェクトの遅延を引き起こしました。
C1 verb /ˈɪnfɪltreɪt/

infiltrate

浸透
Meaning
to secretly enter or gain access to a place or group
Example
The spies managed to infiltrate the enemy base.
スパイたちは敵基地に infiltrate できた。
C1 noun /ˌɪn.trəˈspek.ʃən/

introspection

内省
Meaning
The examination or observation of one's own mental and emotional processes; self-reflection.
Example
Through introspection, she gained insight into her emotions.
内省を通じて、彼女は自分の感情に対する深い洞察を得ました。
C1 noun (plural) /ˈɪndɪˌsiːz/

indices

インデックス
Meaning
plural form of index; statistical measures or reference points used for comparison
Example
Stock market indices fell sharply after the announcement.
発表後、株式市場のインデックスは急落しました。
C1 adverb /ˈɪnwərdli/

inwardly

内面的に
Meaning
In the mind or spirit; not outwardly visible.
Example
She smiled outwardly but inwardly she was worried.
彼女は外見では微笑んだが、内心では心配していた。