infiltrate
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C1 verb /ˈɪnfɪltreɪt/

infiltrate

Meaning
to secretly enter or gain access to a place or group
Example
The spies managed to infiltrate the enemy base.
B2 noun /ˈaɪrəni/

irony

Meaning
a situation that is strange or amusing because it is the opposite of what is expected; the use of words to convey the opposite meaning
Example
The irony of the situation was that the winner forgot his own prize.
C2 noun /ˈɪl.i.æd/

iliad

Meaning
An ancient Greek epic poem attributed to Homer, describing the events of the Trojan War.
Example
Students studied the Iliad to understand Greek mythology and heroism.
B2 verb /ˌɪntərˈfɪər/

interfere

Meaning
to become involved in something that is not your concern; to hinder or obstruct
Example
Parents should not interfere in their children’s personal choices.
B2 noun /ɪsˈlɑːm/

islam

Meaning
the religion founded by the Prophet Muhammad, based on belief in one God (Allah)
Example
Islam emphasizes peace, justice, and compassion.
C1 verb /aɪˈdiː.ə.laɪz/

idealize

Meaning
To regard or represent something as perfect or better than it really is.
Example
Children often idealize their parents.
B2 adjective ˈɪn.tɪ.ɡreɪ.tɪd

integrated

Meaning
Combining or coordinating separate elements so as to provide a harmonious, interrelated whole.
Example
Integrated systems optimize efficiency.
A2 verb /ɪɡˈnɔːr/

ignore

Meaning
to refuse to take notice of; to disregard intentionally
Example
She decided to ignore the rude comments.
B2 noun /ˌɪm.ɪˈteɪ.ʃən/

Imitation

Meaning
the action of using someone or something as a model; a copy of something original
Example
His imitation of the famous actor was so good that everyone burst into laughter.
B1 noun/adjective /ˈɪnstənt/

instant

Meaning
A very short period of time; happening immediately.
Example
He replied in an instant without hesitation.
B1 verb /ˌɪntərˈækt/

interact

Meaning
to communicate or work together with someone or something
Example
Students interact with teachers during class discussions.
B2 adjective, noun /ˌɪn.təlˈɛk.tʃu.əl/

intellectual

Meaning
Relating to the intellect; a person who engages in critical thinking and study.
Example
She enjoys intellectual discussions about philosophy.
B2 noun /ɪnˈspɛktər/

inspector

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.
C2 adjective /ˈɪl bred/

Ill-bred

Meaning
lacking good manners; rude; showing poor upbringing
Example
His ill-bred behavior shocked everyone at the dinner party.
C2 noun /ˌɪntərˈlɒkjətər/

interlocutor

Meaning
a person who takes part in a conversation or dialogue
Example
She was a skilled interlocutor during the debate.
C2 noun /ˌɪntərˈsɛʃən/

intercession

Meaning
the act of intervening or pleading on behalf of another person
Example
The prisoner was released due to the intercession of influential leaders.
B1 noun /ɪnˈstrʌktər/

instructor

Meaning
A person who teaches a subject or skill.
Example
The driving instructor was very patient with new learners.
B2 noun /ˌɪnsɪˈkjʊərɪti/

insecurity

Meaning
lack of confidence or assurance; a state of uncertainty or vulnerability
Example
Her insecurity made her doubt her abilities despite her experience.
A2 verb /ɪˈmædʒɪn/

imagine

Meaning
to form a mental image of; to believe something unreal to be true
Example
Can you imagine living in a different country?
B2 noun /ˈɪɡ.nər.əns/

Ignorance

Meaning
lack of knowledge or information; the state of being uninformed about something
Example
His ignorance about basic computer skills made it difficult for him to find a job.
C1 noun /ɪˈmiːdiəsi/

immediacy

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.
C2 verb /ɪnˈsteɪt/

instate

Meaning
To set up in position, office, or authority.
Example
The board decided to instate her as the new director.
C1 adjective /ˌɪnhɒˈspɪtəbl/

inhospitable

Meaning
Harsh and difficult to live in; unfriendly or unwelcoming to guests.
Example
The desert is an inhospitable environment for most plants.
C2 adjective /ˈɪm.pi.əs/

Impious

Meaning
irreligious; lacking reverence for religion; blasphemous
Example
The impious act shocked the religious community.
C1 adjective /ɪnˈkwɪzɪtɪv/

inquisitive

Meaning
Curious or eager to learn and ask questions.
Example
The inquisitive child asked endless questions about the stars.
C2 verb /ˌɪmpɔːrˈtuːnd/

importuned

Meaning
asked someone persistently and pressingly for something
Example
She importuned her boss for a raise until he finally gave in.
B2 verb /ɪnˈtɛnsɪfaɪ/

intensify

Meaning
To make something stronger, more extreme, or more forceful.
Example
The storm is expected to intensify overnight.
B2 adjective /ɪˈrɪˌspɑn.sə.bəl/

Irresponsible

Meaning
lacking a sense of responsibility; careless
Example
It was irresponsible of him to leave without telling anyone.
C1 noun /ˈɪn.fən.tri/

Infantry

Meaning
soldiers marching or fighting on foot; foot soldiers collectively
Example
The infantry advanced across the battlefield on foot.
A2 adjective/noun /ˈɪndiən/

indian

Meaning
Relating to India, its people, or their culture.
Example
She loves Indian food, especially biryani.
B1 noun ɪnˈvestmənt

investment

Meaning
The action or process of investing money for profit or material result.
Example
Investment in waste management infrastructure is essential.
C2 adjective /ɪnˈɛksərəbl/

inexorable

Meaning
Impossible to stop or prevent; relentless.
Example
The inexorable rise of technology is changing every aspect of life.
C1 verb /ˌɪntəˈsɛkt/

intersect

Meaning
to cross or pass through each other
Example
The two roads intersect at the city center.
C2 adjective /ɪnˈsɛndiˌɛri/

incendiary

Meaning
designed to cause fires or stir up conflict
Example
The politician’s incendiary remarks angered the crowd.
B1 noun aɪˈdɛntɪti

identity

Meaning
The fact of being who or what a person or thing is; the characteristics determining who or what a person or thing is.
Example
The day reinforces our national identity.
C1 noun /ɪnˈædɪkwəsi/

inadequacy

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.
C1 adjective /ɪˈmjuː.tə.bəl/

immutable

Meaning
Unchangeable, permanent, or fixed
Example
The laws of physics are considered immutable.
C1 adjective ˌɪn.krəˈmen.təl

incremental

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.
C1 verb /ˈɪnsjuleɪt/

insulate

Meaning
To protect something by covering it, especially to prevent heat, sound, or electricity from escaping or entering.
Example
The house was insulated to reduce heating costs.
C1 adjective /ɪnˈtjuː.ɪ.tɪv/

intuitive

Meaning
Based on instinctive understanding rather than reasoning.
Example
The software has an intuitive design that makes it easy to use.
B1 verb /ɪnˈvɛnt/

invent

Meaning
to create or design something that has not existed before
Example
Thomas Edison invented the electric bulb.
B2 noun ɪˈlɪtərəsi

illiteracy

Meaning
The inability to read and write; lack of education or knowledge in a particular area.
Example
Illiteracy often leads to poverty and unemployment.
B2 noun ˌɪn.təˈven.ʃən

intervention

Meaning
The action or process of intervening; involvement in a situation to improve or help it.
Example
The intervention of the UN was crucial in resolving the conflict.
C1 adjective /ɪnˈtændʒəbl/

intangible

Meaning
Unable to be touched or grasped; not having a physical presence.
Example
Trust is an intangible quality in relationships.
A1 adjective /ɪmˈpɔː.tənt/

important

Meaning
Of great significance or value; likely to have a profound effect on success, survival, or well-being.
Example
Important steps must be taken to address pollution.
B2 noun ɪnˌdʌstrɪəlaɪˈzeɪʃən

industrialization

Meaning
The development of industries in a country or region on a wide scale.
Example
Industrialization changed the global economy dramatically.
C2 noun /ɪmˈpjuːnɪti/

impunity

Meaning
freedom from punishment or harmful consequences for an action
Example
The dictator ruled with impunity, ignoring international laws.
C2 adjective /ˌɪrɪˈdjuːsəbl/

irreducible

Meaning
impossible to reduce or simplify further
Example
The fraction 3/7 is irreducible.
C2 adjective /ˌɪnɪkˈsprɛsəbl/

inexpressible

Meaning
Too strong or extreme to be expressed in words.
Example
She felt inexpressible joy at the news of her success.
A2 adjective ˌɪn.təˈnæʃ.ən.əl

international

Meaning
Existing, occurring, or carried on between two or more nations and their citizens.
Example
International standards improve competitiveness.
C1 noun /ˌɪnfɪˈdɛləti/

infidelity

Meaning
the act of being unfaithful to a spouse or partner
Example
Their marriage ended due to his infidelity.
C1 noun ɪnˈflɛk.ʃən

inflection

Meaning
The change in pitch or tone of voice when speaking for emphasis.
Example
His inflection kept the audience engaged.
C2 noun /ɪnˈtɛmpərəns/

intemperance

Meaning
Lack of moderation or self-control, especially with drinking or eating.
Example
His intemperance in drinking ruined his health.
C2 noun /ɪnˌtɜːrpəˈleɪʃən/

interpolation

Meaning
The act of inserting something into a text or estimating values within a sequence of data.
Example
The scientist used interpolation to predict the missing data points.
C1 noun ˌɪnˈsaɪtfʊlnɪs

insightfulness

Meaning
The capacity to gain an accurate and deep intuitive understanding of a person or thing.
Example
His insightfulness helped solve the complex problem.
B2 noun /ˈɪntərvəl/

interval

Meaning
a period of time between two events or points; a pause or break in activity
Example
There was a short interval between the two performances.
B2 adjective /ɪnˈædɪkwət/

inadequate

Meaning
Not sufficient or good enough.
Example
The funding was inadequate to complete the project.
C1 noun /ɪnˈdjuːsmənt/

inducement

Meaning
something that persuades or encourages someone to do something
Example
The company offered a bonus as an inducement to employees.
B2 adjective /ˌɪntəˈpɜːsənl/

interpersonal

Meaning
Relating to relationships or communication between people.
Example
He has excellent interpersonal skills and gets along well with others.
C2 adjective /ɪnhɑːrˈmoʊniəs/

Inharmonious

Meaning
lacking harmony; discordant in sound; not in tune
Example
The inharmonious sounds from the broken piano made everyone cover their ears.
C1 verb /ɪnˈsɪnjueɪt/

insinuate

Meaning
To suggest or hint something indirectly and often unpleasantly.
Example
He insinuated that she had lied about her qualifications.
B2 noun /ɪnˈtɛnt/

intent

Meaning
the purpose or reason behind an action; a strong determination to do something
Example
Her intent was to improve the quality of education in the community.
C1 noun /ˌɪn.trəˈvɜːr.ʒən/

introversion

Meaning
The tendency to be inward-looking and shy, preferring solitary activities.
Example
Her introversion made it difficult for her to enjoy large parties.
C1 noun /ɪnˈfɜːrnoʊ/

inferno

Meaning
a large, intense fire that is dangerously out of control
Example
The building turned into an inferno within minutes.
C1 noun /ɪnˈhɛrɪtər/

inheritor

Meaning
a person who receives money, property, or a title when someone dies
Example
She became the inheritor of her family's estate.
C1 noun ɪnˌɛv.ɪ.təˈbɪl.ɪ.ti

inevitability

Meaning
The quality of being certain to happen and impossible to avoid or prevent.
Example
The inevitability of change is a part of life.
C1 adjective ˌɪn.trəˈspek.tɪv

introspective

Meaning
Characterized by or given to introspection; examining one's own thoughts and feelings.
Example
Writers tend to be highly introspective individuals.
C2 verb /ˌɪntərˈpoʊz/

interpose

Meaning
To place or insert between one thing and another; to intervene in a situation.
Example
He quickly interposed himself between the fighters to stop the quarrel.
C1 adjective /ɪnˈɛlɪdʒəbəl/

Ineligible

Meaning
not qualified or entitled to participate or be chosen; unsuitable
Example
Students with poor grades are ineligible for the scholarship program.
C1 verb /ɪmˈpɛrɪl/

imperil

Meaning
To put in danger or at risk.
Example
Reckless driving can imperil the lives of others.
B2 adjective /ˌɪd.iˈɒt.ɪk/

Idiotic

Meaning
extremely stupid; foolish; senseless
Example
His idiotic behavior embarrassed everyone at the meeting.
B2 noun ˈɪn.deks

index

Meaning
An alphabetical list of names, subjects, etc. with references to the places where they occur, typically found at the end of a book; a sign or measure of something.
Example
An index organizes critical data.
B1 abbreviation /ˌaɪˈiː/

ie

Meaning
That is to say; used to clarify or explain something more precisely.
Example
Many amphibians, i.e., frogs and salamanders, can live both in water and on land.
C2 noun /ɪnˈdɛntʃər/

indenture

Meaning
A formal legal agreement, contract, or document, often relating to work or service.
Example
In the 18th century, many workers came under indenture to work overseas.
C1 noun /ɪnˈfɜːməri/

infirmary

Meaning
A hospital or place where the sick or injured are cared for.
Example
The school had an infirmary for minor injuries.
C1 noun /ˌɪnkɑːrˈneɪʃən/

incarnation

Meaning
the embodiment of a deity, spirit, or quality in a physical form
Example
The monk was considered the incarnation of compassion.
C1 noun /ɪnˈsɒm.ni.ə/

Insomnia

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.
C2 adjective /ˌɪməˈmɔːriəl/

immemorial

Meaning
Extending back beyond memory or record; ancient.
Example
The tradition has been followed since time immemorial.
C2 verb /ˌɪnkəˈpæsɪteɪt/

incapacitate

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.
C1 adjective ˌɪn.təˈmɪt.ənt

intermittent

Meaning
Happening irregularly, not continuously.
Example
The rain was intermittent throughout the day.
B2 noun /ɪnˈtɜː.prə.tər/

Interpreter

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.
C1 adverb ɪnˈtrɪn.zɪ.kli

intrinsically

Meaning
In a way that is naturally or inherently part of something's essential nature.
Example
Some people are intrinsically motivated to learn.
C1 adjective /ɪmˈpæsəbəl/

impassable

Meaning
Impossible to travel along or over.
Example
The road became impassable after the heavy snowfall.
A2 adjective /ɪnˈtɛlɪdʒənt/

intelligent

Meaning
Having or showing high mental capacity, quick to learn and understand.
Example
She is one of the most intelligent students in the class.
C2 adjective /ɪnˈeɪliənəbl/

inalienable

Meaning
Unable to be taken away or transferred; absolute and permanent.
Example
Freedom of speech is an inalienable right.
C2 adjective /ˌɪnsəˈpɔːrtəbl̩/

insupportable

Meaning
Too extreme or difficult to be endured.
Example
The heat was insupportable during the long journey.
C1 adjective /ˌɪntərˈtʃeɪndʒəbl/

interchangeable

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.
B2 noun /ɪnˈvɒlvmənt/

involvement

Meaning
the act of taking part in something
Example
His involvement in the project was crucial.
C2 adjective /ɪnˈɡreɪʃiˌeɪtɪŋ/

ingratiating

Meaning
Charming or flattering in a way intended to gain favor.
Example
His ingratiating smile made everyone trust him quickly.
C1 adjective /ɪnˈsɛp(ə)rəbəl/

inseparable

Meaning
Unable to be separated or always together.
Example
The two friends have been inseparable since childhood.
C2 adverb /ˌɪnsəʊˈmʌtʃ/

insomuch

Meaning
to such an extent
Example
He was insomuch tired that he could hardly stand.
C2 adjective /ɪnˈkɒrɪdʒəbəl/

incorrigible

Meaning
incapable of being corrected, improved, or reformed
Example
He is an incorrigible optimist who never loses hope.
C1 adjective /ɪnˈtɛlɪdʒəbl/

intelligible

Meaning
Able to be understood; clear enough to be comprehended.
Example
Her speech was barely intelligible over the noise.
B1 adjective /ɪnkəˈrɛkt/

incorrect

Meaning
not correct or accurate
Example
The information you provided was incorrect.
C2 adjective /ɪnˈtɛsteɪt/

intestate

Meaning
Having died without leaving a valid will.
Example
She died intestate, so her assets were distributed by law.
C2 adjective /ˌɪntəˈrɒɡətəri/

interrogatory

Meaning
expressed in the form of a question; relating to questioning
Example
The lawyer’s interrogatory tone made the witness uncomfortable.
C2 adjective /ɪnˈsɛptɪv/

inceptive

Meaning
Relating to or marking the beginning or initial stage of something.
Example
The inceptive phase of the project was marked by enthusiastic planning.
C1 adjective /ɪnˈveɪsɪv/

invasive

Meaning
Tending to spread harmfully, intruding aggressively, or encroaching beyond proper boundaries.
Example
The doctor explained that the procedure was minimally invasive.
B2 verb /ɪnˈspekt/

inspect

Meaning
to examine something carefully to check for problems or faults
Example
The engineer will inspect the building for structural damage.
C1 noun /ɪnˈdʒʌŋkʃən/

injunction

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.
B2 noun /ɪmˈpeɪʃəns/

impatience

Meaning
The state of being quickly irritated or unable to wait calmly.
Example
His impatience grew as the meeting dragged on.
C2 verb /ɪmˈpjuːt/

impute

Meaning
to attribute a fault or responsibility to someone
Example
They imputed the company's success to good leadership.
C1 adjective /ɪnˈsɒlvənt/

insolvent

Meaning
unable to pay debts owed
Example
The insolvent firm could not meet its financial obligations.
A2 noun /ˌɪn.trəˈdʌk.ʃən/

introduction

Meaning
the action of introducing something or someone; an opening or beginning part
Example
The professor gave a brief introduction before starting the lecture.
C2 verb /ɪnˈveɪ/

inveigh

Meaning
To speak or write about something with great hostility and criticism.
Example
He inveighed against the corruption in government.
A2 noun, verb /ˈɪʃuː/

issue

Meaning
A problem, topic, or the act of supplying or distributing something.
Example
The magazine will issue a new edition next week.
C1 noun /ˈɪŋ.krə.mənt/

Increment

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.
C1 noun /ɪmˈpɛd.ɪ.mənt/

impediment

Meaning
A hindrance or obstruction in doing something; something that prevents progress.
Example
Lack of funds is a major impediment to the project.
B2 noun /ɪnˈfek.ʃən/

Infection

Meaning
the process of infecting or the state of being infected; a disease caused by germs
Example
The doctor prescribed antibiotics to treat the bacterial infection in her throat.
C1 noun /ˌɪnkəmˌpætəˈbɪlɪti/

incompatibility

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.
C1 noun /ɪnˈdɪf.ər.əns/

Indifference

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.
C2 adjective /ˌɪndɪˈtɜːrmənət/

indeterminate

Meaning
Not exactly known, defined, or established; vague or uncertain.
Example
The project was delayed for an indeterminate amount of time.
C2 verb /ɪmˈpjuːn/

impugn

Meaning
to dispute the truth, validity, or honesty of a statement or motive
Example
The lawyer tried to impugn the credibility of the witness.
B1 adjective /ˌɪnɪkˈspɛnsɪv/

Inexpensive

Meaning
not costing a lot of money; affordable; budget-friendly
Example
This restaurant offers delicious and inexpensive meals for students.
B2 adjective /ɪmˈprɒp.ər/

Improper

Meaning
inappropriate; incorrect; not suitable
Example
It would be improper to discuss personal matters in a business meeting.
C2 adjective /ˌɪnkəˈməʊdiəs/

incommodious

Meaning
Uncomfortably small, cramped, or inconvenient.
Example
We had to stay in an incommodious room during the trip.
C1 adverb /ɪnˈvɜːrs.li/

Inversely

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.
C1 adjective /ɪmˈplɔːzəbl/

implausible

Meaning
Not seeming reasonable or probable; unlikely to be true.
Example
The story she told was so implausible that no one believed her.
C2 noun /ɪˈluːmɪnənt/

illuminant

Meaning
A substance or device that produces light.
Example
The lamp acted as an illuminant in the dark cave.
C1 noun /ˈɪn.trə.vɜːrt/

introvert

Meaning
A person who tends to be shy and prefers spending time alone rather than in groups.
Example
As an introvert, he preferred reading over attending parties.
C2 adjective /aɪˈtɪnərənt/

itinerant

Meaning
Traveling from place to place, especially for work or duty.
Example
The itinerant teacher moved from village to village to educate children.