infiltration
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C1 noun ˌɪn.fɪlˈtreɪ.ʃən

infiltration

浸透、秘密のアクセス
Meaning
The process of entering or gaining access to an organization or place surreptitiously.
Example
Cybersecurity prevents infiltration into sensitive data.
サイバーセキュリティは、機密データへの浸透を防ぎます。
C1 verb /ɪˈmɔːrtəlaɪz/

immortalize

不朽の
Meaning
to preserve the memory of someone or something forever
Example
The statue was built to immortalize the hero’s sacrifice.
その像は、英雄の犠牲を永遠にするために建てられました。
B2 adjective /ˌɪnkənˈsɪstənt/

inconsistent

一貫性がない
Meaning
Not staying the same throughout; lacking harmony or regularity.
Example
His answers were inconsistent and confusing.
彼の答えは一貫性がなく、混乱を招いた。
C2 adjective/verb /ɪnˈkɑːrneɪt/

incarnate

具現化
Meaning
to embody or represent in human form; in flesh
Example
She is kindness incarnate.
彼女は親切さの具現化です。
B2 noun /ɪnˈtɛnsəti/

intensity

強度
Meaning
The quality of being extreme, strong, or forceful in degree.
Example
The intensity of the storm frightened the villagers.
嵐の強度は村人たちを驚かせた。
C2 noun /ɪˌledʒ.əˈbɪl.ə.ti/

Illegibility

読みにくさ
Meaning
the quality of being impossible or difficult to read; unclear writing or print
Example
The doctor's handwriting was famous for its illegibility among the pharmacy staff.
医者の手書きは薬局のスタッフの間でその読みにくさで有名でした。
A1 conjunction /ɪf/

if

もし
Meaning
used to introduce a condition or supposition
Example
If it rains tomorrow, we will stay home.
もし明日雨が降ったら、私たちは家にいます。
C2 adjective /ɪnˈsuːsiənt/

insouciant

無頓着
Meaning
Showing a casual lack of concern; carefree.
Example
He gave an insouciant shrug and walked away.
彼は無頓着に肩をすくめて、歩き去った。
C1 adjective /ɪnˈsɪstənt/

insistent

執拗な
Meaning
demanding something firmly and refusing to accept no
Example
The child was insistent on getting a new toy.
その子供は新しいおもちゃを手に入れることに執拗だった。
B2 noun ɪnˈfleɪʃən

inflation

インフレーション
Meaning
A general increase in prices and fall in the purchasing value of money.
Example
Inflation erodes the purchasing power of consumers.
インフレーションは消費者の購買力を減少させる。
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 adjective /ɪnˈhjuːmən/

Inhuman

非人道的
Meaning
lacking human qualities of compassion and mercy; cruel or barbaric
Example
The prisoners were kept in inhuman conditions.
囚人たちは非人道的な状況で収容されていました。
C2 verb /ɪnˈɡrɑːft/

ingraft

根付ける
Meaning
To implant or fix deeply, often used in the sense of grafting an idea or quality.
Example
The teacher tried to ingraft good manners in the students.
先生は生徒たちに良いマナーを根付かせようとした。
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。
A2 noun /ˈɪlnəs/

illness

病気
Meaning
A condition of being unwell or suffering from a disease.
Example
She missed school due to a serious illness.
彼女は深刻な病気のため学校を休んだ。
C2 adjective /ɪnˈɡreɪʃiˌeɪtɪŋ/

ingratiating

お世辞を言う
Meaning
Charming or flattering in a way intended to gain favor.
Example
His ingratiating smile made everyone trust him quickly.
彼のお世辞を言う笑顔は、すべての人々に彼を素早く信頼させた。
B2 adjective /ˈɪnfɪnɪt/

infinite

無限
Meaning
limitless or endless in space, extent, or number
Example
The universe is often described as infinite.
宇宙はしばしば無限だと説明されます。
C2 verb /ɪˈniː.bri.eɪt/

inebriate

Meaning
to intoxicate; to make someone drunk
Example
The strong wine was enough to inebriate even the most experienced drinker.
B2 noun /ɪnˈspɛktər/

inspector

検査官
Meaning
An official employed to ensure regulations are obeyed or standards are met.
Example
The inspector carefully checked the restaurant's kitchen for hygiene standards.
検査官はレストランのキッチンを衛生基準に従って慎重に確認しました。
C1 adjective /ɪmˈprɒbəbl/

improbable

あり得ない
Meaning
Not likely to be true or to happen.
Example
It seems improbable that he will arrive on time.
彼が時間通りに到着するのはあり得ないようだ。
A2 adjective /ɪnˈtɛlɪdʒənt/

intelligent

賢い
Meaning
Having or showing high mental capacity, quick to learn and understand.
Example
She is one of the most intelligent students in the class.
彼女はクラスで最もインテリジェントな学生の一人です。
B1 adjective /ɪmˈpruːvd/

improved

改善された
Meaning
made better or enhanced in quality or condition
Example
Her health has significantly improved since last month.
彼女の健康は先月から大きく改善されました。
C1 adjective /ɪmˈplɔːzəbl/

implausible

信じがたい
Meaning
Not seeming reasonable or probable; unlikely to be true.
Example
The story she told was so implausible that no one believed her.
彼女が話した話はあまりにも信じられないほどで、誰も彼女を信じなかった。
C2 verb /ˌɪnkəˈpæsɪteɪt/

incapacitate

無力化する
Meaning
to deprive someone or something of the ability or strength to function
Example
The severe injury incapacitated the player for the rest of the season.
その重傷はプレーヤーをシーズンの残りの期間無力化させた。
B2 noun ˌɪr.ɪˈɡeɪ.ʃən

irrigation

灌漑
Meaning
The artificial application of water to land or soil.
Example
Irrigation systems improve crop yields in dry regions.
灌漑システムは乾燥した地域で作物の収穫量を増加させます。
B2 adjective /ɪnˈkluːsɪv/

inclusive

包括的
Meaning
Including all the services, facilities, or items normally expected or required; not excluding any section of society or any party involved.
Example
Inclusive growth benefits all sections of society.
包括的な成長は、社会のすべての層に利益をもたらします。
C1 verb /ɪnˈvoʊk/

invoke

呼び出す
Meaning
to call upon a higher power, authority, or principle for help, support, or justification
Example
The lawyer invoked the constitution to defend his client.
弁護士は憲法を引き合いに出して自分のクライアントを守った。
B2 noun /ˌɪntəˈrʌpʃən/

interruption

中断
Meaning
the act of stopping or breaking the continuity of something; a pause caused by an external action
Example
The meeting was delayed due to an unexpected interruption.
予期しない中断のため会議は遅れた。
C2 noun /ˌɪkθiˈɒlədʒɪst/

ichthyologist

魚類学者
Meaning
A scientist who studies fish.
Example
The ichthyologist discovered a new species of fish in the river.
魚類学者は川で新しい魚の種を発見しました。
B2 verb /ɪtʃ/

itch

かゆみ
Meaning
to feel an urge to scratch; to have a restless desire
Example
My skin itches from the mosquito bites.
蚊に刺されて肌がかゆいです。
B2 noun /ɪmˈpɒlɪtnəs/

impoliteness

無礼さ
Meaning
lack of good manners or courtesy; rude behavior
Example
His impoliteness towards the guests shocked everyone.
彼の客に対する無礼さは皆を驚かせた。
B2 adjective /ɪnˈfɪə.ri.ər/

inferior

劣等
Meaning
Of lower quality, rank, or status.
Example
This material is inferior to the one we used before.
この素材は以前使ったものより劣っています。
C2 adjective /ɪmˈpɪəriəs/

imperious

横柄な
Meaning
Arrogantly domineering or overbearing.
Example
Her imperious tone made it hard for others to argue.
彼女の横柄な口調は他の人々が議論するのを難しくしました。
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。
C2 adjective /ˌɪnkoʊˈɜːrsəbl̩/

incoercible

強制できない
Meaning
Not capable of being forced, compelled, or restrained.
Example
Her incoercible spirit inspired others to fight for justice.
彼女の強制できない精神は他の人々に正義のために戦うようにインスパイアした。
C2 noun /ˌɪmpəˈtjuːəsəti/

impetuosity

衝動性
Meaning
The quality of being rash or impulsive.
Example
His impetuosity often got him into trouble.
彼の衝動性はしばしば彼を問題に巻き込んだ。
C1 adjective /ɪnˈsɛp(ə)rəbəl/

inseparable

切り離せない
Meaning
Unable to be separated or always together.
Example
The two friends have been inseparable since childhood.
二人の友達は子供の頃から切り離せないです。
A1 pronoun /ɪt/

it

それ
Meaning
used to refer to a thing, animal, or idea previously mentioned or easily identified
Example
It is raining outside.
外では雨が降っています。
B1 adjective ˈɪnəveɪtɪv

innovative

革新的な
Meaning
Featuring new methods; advanced and original
Example
Innovative strategies are required to combat pollution.
革新的な戦略が汚染との戦いに必要です。
A1 pronoun /ɪts/

its

それの
Meaning
Belonging to or associated with a thing previously mentioned.
Example
The company changed its logo last year.
会社は昨年そのロゴを変更しました。
B2 adjective /ɪnˈtɛns/

intense

強烈
Meaning
Of extreme force, degree, or strength.
Example
She felt intense pain after the accident.
事故後、彼女は強烈な痛みを感じました。
B2 noun /ˌaɪ.səˈleɪ.ʃən/

Isolation

隔離
Meaning
the process or fact of isolating or being isolated; separation from other people or things
Example
The patient was kept in isolation to prevent the spread of the infectious disease.
患者は感染症の拡大を防ぐために隔離されました。
C1 adjective /ɪˈrɛfjʊtəbəl/

Irrefutable

反論できない
Meaning
impossible to deny or disprove; undeniable
Example
The evidence against him was irrefutable.
彼に対する証拠は否定できないものでした。
B2 noun /ˈɪm.pʌls/

Impulse

衝動; 突然の欲求
Meaning
a sudden strong and unreflective urge or desire to act; a driving force or motivation
Example
She bought the expensive dress on impulse and later regretted the purchase.
彼女は衝動で高価なドレスを買い、後でその購入を後悔しました。
B2 verb /ɪnˈsʌlt/

insult

侮辱する
Meaning
to speak or act in a way that hurts someone's feelings or shows disrespect
Example
He felt insulted by her rude comments.
彼は彼女の失礼なコメントで侮辱されたと感じた。
C2 adjective /ˌɪndɪˈfætɪɡəbl̩/

indefatigable

疲れ知らず
Meaning
persisting tirelessly; incapable of being fatigued
Example
Her indefatigable spirit kept the team motivated during the long project.
彼女の疲れ知らずの精神が、長いプロジェクトを通してチームを励ましました。
C2 adjective /aɪˈtɪnərənt/

itinerant

旅する
Meaning
Traveling from place to place, especially for work or duty.
Example
The itinerant teacher moved from village to village to educate children.
その旅する教師は村から村へと移動して子供たちに教育をしていました。
C1 adjective ɪn ˈfleɪ.ʃə.ner.i

inflationary

インフレ的
Meaning
Characterized by or tending to cause monetary inflation; relating to rising prices.
Example
The government took measures to control inflationary pressures.
政府はインフレ圧力を制御するために措置を講じた。
C2 adjective /ɪmˈperɪʃəbəl/

Imperishable

不滅の; 永遠の; 朽ちない
Meaning
not subject to decay; lasting forever; eternal
Example
The imperishable beauty of classical art continues to inspire generations.
古典芸術の不滅の美しさは、世代を超えてインスピレーションを与え続けています。
C2 adjective /ɪnˈsɪpɪd/

insipid

味気ない
Meaning
lacking flavor, interest, or excitement; dull
Example
The soup was insipid and needed more seasoning.
スープは味気なく、もっと調味料が必要でした。
C1 adverb /ɪnˈvɜːrs.li/

Inversely

逆に; 反対に
Meaning
in a way that is opposite or contrary; in reverse order or manner
Example
The price of goods is inversely related to their availability in the market.
商品の価格は市場での入手可能性に逆に関連しています。
C2 noun /ˌɪnədˈvɜːrtəns/

inadvertence

不注意
Meaning
Failure to pay attention; carelessness.
Example
The error happened through sheer inadvertence.
エラーは単なる不注意で発生しました。
C2 verb /ɪnˈdɒktrɪˌneɪt/

indoctrinate

教義を押し付ける
Meaning
To teach someone to fully accept a set of beliefs or ideas without question.
Example
The regime tried to indoctrinate the youth with propaganda.
その政権は宣伝を通じて若者を洗脳しようとした。
B2 noun ˌɪn.stəˈleɪ.ʃən

installation

インストール
Meaning
The action or process of installing someone or something, or of being installed.
Example
The installation of the submarine cable is almost complete.
海底ケーブルのインストールはほぼ完了しています。
C1 adjective ˌɪdiəsɪnˈkrætɪk

idiosyncratic

奇妙で個人的な
Meaning
Relating to idiosyncrasy; peculiar or individual.
Example
His idiosyncratic behavior set him apart from his colleagues.
彼の独特な行動は彼を同僚たちから区別させた。
C2 adjective /ˌɪnkəmˈbʌstəbl/

incombustible

不燃
Meaning
Not capable of catching fire or burning.
Example
This material is incombustible and safe for construction.
この材料は燃えません、安全に建設に使用できます。
B2 verb /ɪnˈtriːɡ/

intrigue

魅了する
Meaning
to arouse curiosity or interest; to make someone fascinated
Example
The mystery novel will intrigue any reader.
ミステリー小説はすべての読者を魅了するでしょう。
B1 verb ˈɪndɪkeɪts

indicates

示す
Meaning
Point out; show; be a sign or symptom of; suggest as a desirable or necessary course of action.
Example
The rising trend indicates an urgent need for action.
上昇している傾向は、行動が急務であることを示しています。
B2 adjective /ˌɪn.trəˈdʌk.tər.i/

introductory

導入の
Meaning
Serving as an introduction; preliminary or preparatory.
Example
The professor gave an introductory lecture on economics.
教授は経済学についての導入の講義を行いました。
C1 noun ɪnˈsɒl.vən.si

insolvency

破産
Meaning
The state of being unable to pay debts owed; bankruptcy.
Example
The company declared insolvency after years of losses.
その会社は多くの損失の後、破産を宣言した。
B1 adjective ɪnˈdʌs.tri.əl

industrial

工業的な
Meaning
Relating to or characterized by industry.
Example
Industrial sectors boost exports.
工業部門は輸出を促進する。
C1 noun /ˌɪndɪˈdʒɛstʃən/

indigestion

Meaning
Discomfort or pain in the stomach associated with difficulty in digesting food.
Example
He avoided spicy food because it often gave him indigestion.
C1 verb /ɪˈluːmɪneɪt/

illuminate

照らす
Meaning
To light up or make something clearer.
Example
Streetlights illuminate the road at night.
街路灯が夜に道路を照らします。
C1 adjective /ɪnˈtræk.tə.bəl/

intractable

管理不能
Meaning
Difficult or impossible to manage, control, or solve.
Example
The conflict has become an intractable problem.
その対立は管理不能な問題になった。
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。
C2 noun /ˌɪntərˈsɛsər/

intercessor

仲介者
Meaning
a person who intervenes or pleads on behalf of another
Example
He acted as an intercessor to resolve the conflict between the two families.
彼は二つの家族間の対立を解決するために仲介者として行動しました。
A2 adjective /ˈɪntrəstɪd/

interested

興味がある
Meaning
Showing curiosity or concern about something.
Example
She is very interested in learning new languages.
彼女は新しい言語を学ぶことにとても興味がある。
C1 adjective /ɪmˈpɜːrsənl/

impersonal

無個性
Meaning
not influenced by, showing, or involving personal feelings; lacking human warmth or emotion
Example
The letter was written in a very impersonal style.
その手紙は非常に無個性的なスタイルで書かれていました。
C2 verb /ɪˈmjʊər/

immure

閉じ込める
Meaning
to confine or enclose someone against their will
Example
The prisoner was immured in a dark cell.
囚人は暗い監房に閉じ込められた。
C2 verb /ɪˈnjʊər/

inure

慣れる
Meaning
To become accustomed to something, especially something unpleasant.
Example
Soldiers quickly became inured to the harsh conditions.
兵士たちはすぐに過酷な状況に慣れました。
B1 verb /ˌɪntərˈækt/

interact

交流する
Meaning
to communicate or work together with someone or something
Example
Students interact with teachers during class discussions.
学生は授業のディスカッション中に教師と交流します。
B2 noun ˌɪmplɪmenˈteɪʃən

implementation

実行
Meaning
The process of putting a decision or plan into effect; execution.
Example
Proper implementation of policies is crucial.
方針の適切な実行は重要です。
A1 adjective /ˈɪntrəstɪŋ/ or /ˈɪntəˌrɛstɪŋ/

interesting

面白い
Meaning
Arousing curiosity or attention; holding one’s interest.
Example
The documentary about space was very interesting.
宇宙についてのドキュメンタリーはとても面白かった。
C1 adjective /ˈɪmpjəd(ə)nt/

impudent

無礼な、厚かましい
Meaning
not showing due respect for another person; rude
Example
The impudent child talked back to the teacher.
その無礼な子供は先生に逆らった。
B1 adjective /ɪnˈtɜːrnəl/

internal

内部
Meaning
situated inside; relating to the inside or inner part of something
Example
The company is conducting an internal audit this month.
その会社は今月内部監査を行っています。
B1 adjective /ˈɪnəsənt/

Innocent

無実の; 純粋な; 無害な
Meaning
free from guilt or sin; pure; harmless; naive
Example
The innocent child had no idea that her parents were planning a surprise party.
その無実の子供は、両親がサプライズパーティーを計画していることを知りませんでした。
B2 verb /ɪnˈfɜːr/

infer

Meaning
to conclude or deduce something from evidence and reasoning rather than from explicit statements
Example
From his silence, I inferred that he was not happy with the decision.
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 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 noun /ˈɪntərˌluːd/

interlude

間奏
Meaning
A short period of time that comes between two events; an interval.
Example
There was a brief musical interlude between the two acts of the play.
演劇の二つの幕の間に短い音楽の間奏がありました。
C2 verb /ɪnˈdɛmnɪfaɪ/

indemnify

Meaning
to compensate someone for harm or loss; to secure against future damage or cost
Example
The insurance company agreed to indemnify the client for the damages.
C1 noun /ɪnˈfɜːrnoʊ/

inferno

火災
Meaning
a large, intense fire that is dangerously out of control
Example
The building turned into an inferno within minutes.
その建物は数分で火災に変わった。
B2 adjective aɪˈkɒnɪk

iconic

象徴的な
Meaning
Very famous or popular, especially being considered to represent particular opinions or a particular time.
Example
The line "It was the best of times..." is iconic.
"それは最良の時代だった…"というセリフは象徴的です。
C2 verb /ɪmˈpeɪl/

impale

突き刺す
Meaning
to pierce or fix something with a sharp object
Example
The knight was impaled by the enemy’s spear.
騎士は敵の槍で突き刺さった。
B2 adverb /aɪˈrɒnɪkli/

ironically

皮肉にも
Meaning
in a way that is contrary to what is expected or intended
Example
Ironically, the fire station burned down.
皮肉にも、消防署が焼け落ちた。
C1 noun /ˌɪntərˈmɪʃən/

intermission

休憩
Meaning
A pause or break, especially during a performance or event.
Example
The play had a twenty-minute intermission.
その劇には20分間の休憩がありました。
C1 noun /ˌɪməˈrælɪti/

immorality

不道徳
Meaning
the quality of being immoral; behavior that violates accepted moral standards
Example
The community condemned the immorality of the corrupt officials.
地域社会は腐敗した役人の不道徳を非難した。
C1 adjective ɪnɪɡˈzɔːstɪbəl

inexhaustible

尽きることのない
Meaning
Unable to be used up or worn out; limitless.
Example
His inexhaustible energy allowed him to work tirelessly on his projects.
彼の尽きることのないエネルギーは、彼がプロジェクトに休むことなく取り組むことを可能にしました。
C2 noun /ɪnˈɛrənsi/

inerrancy

無謬性
Meaning
the belief or quality of being free from error; absolute correctness
Example
Some religious groups strongly affirm the inerrancy of their sacred texts.
いくつかの宗教団体は、自分たちの聖典の誤りのなさを強く主張しています。
B2 adverb /ɪnˈɛvɪtəbli/

inevitably

避けられない
Meaning
in a way that cannot be avoided or prevented
Example
Inevitably, the team faced challenges during the project.
避けられないことに、チームはプロジェクト中に挑戦に直面しました。
C1 noun /ɪnˈdɪf.ər.əns/

Indifference

無関心; 無関心さ; アパシー
Meaning
lack of interest, concern, or sympathy; the state of not caring about something
Example
His indifference to his studies resulted in poor grades throughout the semester.
彼の学業に対する無関心さが、学期中ずっと悪い成績をもたらした。
C2 noun /ˌɪlɪbəˈræləti/

illiberality

不寛容
Meaning
The quality of being illiberal; lack of tolerance or generosity.
Example
The illiberality of the new laws alarmed the citizens.
新しい法律の不寛容が市民を驚かせました。
C1 adjective /ˈɪnbɔːrn/

Inborn

生まれつきの; 生来の; 内在的な
Meaning
existing from birth; natural; inherent
Example
She has an inborn talent for music.
彼女は音楽のための生まれつきの才能を持っています。
C2 adjective /ˌɪɡ.nəˈmɪn.i.əs/

ignominious

不名誉な
Meaning
Marked by shame, disgrace, or humiliation.
Example
The team suffered an ignominious defeat in the finals.
チームは決勝で不名誉な敗北を喫した。
C1 verb /ɪnˈfleɪt/

inflate

膨らませる；水増しする
Meaning
to fill with air or gas so it expands; to increase excessively or artificially
Example
The mechanic inflated the tire to the correct pressure.
整備士はタイヤを適切な空気圧まで膨らませた。
B2 noun ɪnˌdʌstrɪəlaɪˈzeɪʃən

industrialization

産業化
Meaning
The development of industries in a country or region on a wide scale.
Example
Industrialization changed the global economy dramatically.
産業化は世界経済を劇的に変えました。
B2 noun /ɪnˈvɒlvmənt/

involvement

関与
Meaning
the act of taking part in something
Example
His involvement in the project was crucial.
彼のプロジェクトへの関与は重要だった。
B1 verb /ɪnˈkriːst/

increased

増加した
Meaning
became greater in size, amount, or degree
Example
The company's revenue increased last year.
会社の収益は昨年増加しました。
C2 noun /ɪnˈɡrætɪˌtjuːd/

ingratitude

恩知らず
Meaning
Lack of gratitude; failure to show thanks or appreciation.
Example
His ingratitude hurt her feelings after all she had done for him.
彼の恩知らずは、彼女が彼のために多くのことをした後、彼女の気持ちを傷つけた。
A2 noun/verb /ˈɪntrəst/ or /ˈɪntəˌrɛst/

interest

興味 / 利子
Meaning
A feeling of curiosity or concern about something; or money paid for the use of borrowed money.
Example
He showed great interest in learning new languages.
彼は新しい言語を学ぶことに大きな興味を示しました。
C1 noun /ˌɪrɪˌspɒnsəˈbɪləti/

irresponsibility

無責任
Meaning
lack of responsibility or accountability; failure to act in a reliable or sensible way
Example
The accident was caused by his irresponsibility at work.
その事故は彼の職場での無責任さが原因でした。
B1 adjective /ˌɪnɪkˈspɛnsɪv/

Inexpensive

安い; 手頃な; 経済的
Meaning
not costing a lot of money; affordable; budget-friendly
Example
This restaurant offers delicious and inexpensive meals for students.
このレストランは学生のためにおいしくて安い食事を提供しています。
C1 verb /ˈɪrɪˌɡeɪt/

irrigate

灌漑する
Meaning
to supply water to land or crops; to wash out a wound with water
Example
Farmers irrigate their fields during dry seasons.
農家は乾季に畑に灌漑を行います。
B2 verb /ˈɪr.ɪ.teɪt/

irritate

イライラさせる
Meaning
To make someone annoyed or angry; to cause discomfort or inflammation.
Example
Rubbing your eyes can irritate them.
目をこすると、それが刺激になることがあります。
A2 noun /ˈɪʃ.uːz/

issues

問題
Meaning
Important topics or problems for debate or discussion.
Example
Health issues from pollution are increasing.
汚染による健康問題が増加しています。
C2 noun /ˈɪmɪˌteɪtər/

imitator

模倣者
Meaning
a person who copies the behavior, style, or actions of others
Example
He became famous as an imitator of popular singers.
彼は人気のある歌手の模倣者として有名になった。
C2 verb /ɪnˈdʒɛst/

ingest

摂取する
Meaning
To take food, drink, or another substance into the body, usually by swallowing.
Example
The patient must ingest the medicine with water.
患者は水と一緒に薬を摂取する必要があります。
B2 adjective /ˌɪnstɪˈtjuːʃənl/

institutional

制度的
Meaning
Relating to an organization or established practice.
Example
The government made several institutional reforms in education.
政府は教育においていくつかの制度的改革を実施しました。
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。
B2 noun /ˌɪnstəˈbɪləti/

instability

不安定
Meaning
lack of stability or balance; tendency to change, fail, or collapse easily
Example
Political instability has slowed economic growth in the region.
政治的な不安定さが地域の経済成長を遅らせた。
C1 noun /ˌɪn.trəˈvɜːr.ʒən/

introversion

内向
Meaning
The tendency to be inward-looking and shy, preferring solitary activities.
Example
Her introversion made it difficult for her to enjoy large parties.
彼女の内向的な性格は、大きなパーティーを楽しむのを難しくした。
C1 adjective /ˌɪnstənˈteɪniəs/

instantaneous

即時
Meaning
Happening immediately, without any delay.
Example
The change in temperature was almost instantaneous.
温度の変化はほぼ即時でした。
C2 adjective /ɪˈnɪmɪkəl/

inimical

敵対的 / 不利な
Meaning
tending to obstruct or harm; unfriendly or hostile
Example
The policy was inimical to the country's economic growth.
その政策は国の経済成長に不利だった。
C2 verb /aɪˈtɪnəˌreɪt/

itinerate

旅行する
Meaning
To travel from place to place, usually for the purpose of work or preaching.
Example
The missionary itinerated throughout the region to spread the message.
伝道師は地域を巡り、メッセージを広めました。
C2 adjective /ˌɪnkənˈsɪdərəbl/

inconsiderable

取るに足らない
Meaning
Too small or unimportant to be worth considering.
Example
The donation was not inconsiderable, though smaller than expected.
寄付は取るに足らなかったが、予想よりも小さかった。
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 /ɪˈnɜː.ʃə/

Inertia

慣性; 活動の欠如
Meaning
a tendency to do nothing or remain unchanged; lack of activity or movement
Example
The team's inertia prevented them from adapting to the rapidly changing market conditions.
チームの慣性は、急速に変化する市場の状況に適応するのを妨げました。
C1 noun /ɪmˈpɛd.ɪ.mənt/

impediment

障害
Meaning
A hindrance or obstruction in doing something; something that prevents progress.
Example
Lack of funds is a major impediment to the project.
資金不足はプロジェクトの大きな障害です。
B2 noun /ɪnˈtɜː.prə.tər/

Interpreter

通訳者; 翻訳者;
Meaning
a person who translates orally from one language into another; someone who explains meaning
Example
The international conference hired professional interpreters to translate speeches in real time.
国際会議は、スピーチをリアルタイムで翻訳するためにプロの通訳者を雇いました。
B2 adjective /ɪnˈtɛnsɪv/

intensive

集中的
Meaning
Involving a lot of effort, energy, or concentration in a short period of time.
Example
She attended an intensive English course before moving abroad.
彼女は海外に引っ越す前に、集中的な英語コースを受講しました。
B1 adjective /ɪmˈpres.ɪv/

Impressive

印象的な
Meaning
striking; remarkable; having the ability to impress
Example
Her impressive performance earned her a standing ovation.
彼女の印象的な演技はスタンディングオベーションを受けた。