infiltrate
All a b c d e f g h i j k l m n o p q r s t u v w x y z
All CEFR A1 A2 B1 B2 C1 C2
Content locale
EN English BN Bengali HI Hindi ES Spanish FR French DE German RU Russian ZH Chinese JA Japanese
All Vocabulary Cards All Vocabularies
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.
C1 adjective ɪnɪɡˈzɔːstɪbəl

inexhaustible

Meaning
Unable to be used up or worn out; limitless.
Example
His inexhaustible energy allowed him to work tirelessly on his projects.
C1 noun ɪˌræʃ.ənˈæl.ɪ.ti

irrationality

Meaning
The quality of being illogical or unreasonable; lack of rational thought.
Example
His decision was driven by complete irrationality.
C1 adjective; noun /ɪˈmɔːrtl/

immortal

Meaning
living forever; never dying; lasting forever in fame or memory
Example
Legends often describe heroes as immortal beings who never die.
C1 verb /ɪˈluːmɪneɪt/

illuminate

Meaning
To light up or make something clearer.
Example
Streetlights illuminate the road at night.
C1 adjective /ɪmˈpæsəbəl/

impassable

Meaning
Impossible to travel along or over.
Example
The road became impassable after the heavy snowfall.
C1 noun /ɪmˈpjʊərəti/

impurity

Meaning
the state of being unclean or contaminated; a substance that makes something impure
Example
The scientist removed every impurity from the water sample.
C1 verb ɪˈnɪʃɪeɪtɪd

initiated

Meaning
Caused a process or action to begin; started something.
Example
The project was initiated to enhance marine biodiversity.
C1 verb /ɪmˈplɔːr/

implore

Meaning
To beg someone earnestly or desperately to do something.
Example
She implored him to stay with her.
C1 noun /ˈɪnkjʊˌbeɪtər/

incubator

Meaning
a device or environment that provides suitable conditions for eggs, cells, or infants to develop
Example
The premature baby was placed in an incubator for care.
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 /ɪˈlɪsɪt/

illicit

Meaning
Forbidden by law, rules, or custom.
Example
The police shut down the illicit drug operation.
C1 noun /ˌɪn.dɪˈsɪʒ.ən/

Indecision

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.
C1 verb /ɪnˈdʌkt/

induct

Meaning
to formally admit someone into a position, organization, or office
Example
She was inducted into the university's honor society.
C1 noun /ˌɪnækˈtɪvɪti/

inactivity

Meaning
the state of not being active physically or mentally; lack of action
Example
Prolonged inactivity can negatively affect both physical and mental health.
C1 verb /ɪmˈpiːd/

impede

Meaning
To obstruct or hinder the progress or development of something.
Example
Lack of funds can impede business growth.
C1 noun ˌɪnfrəˈstrʌktʃərəl dɪˈveləpmənt

infrastructural development

Meaning
The process of building and improving the basic physical and organizational structures and facilities needed for the operation of a society or enterprise.
Example
Infrastructural development is necessary for efficient recycling.
C1 adjective /ɪmˈprɒmp.tjuː/

impromptu

Meaning
Done without being planned, organized, or rehearsed; spontaneous.
Example
He gave an impromptu speech at the event.
C1 noun ɪnˈsɒl.vən.si

insolvency

Meaning
The state of being unable to pay debts owed; bankruptcy.
Example
The company declared insolvency after years of losses.
C1 noun /ˌɪmpɔːrˈteɪʃən/

importation

Meaning
The act of bringing goods or services into a country from abroad
Example
The importation of luxury goods is strictly regulated.
C1 adjective /ɪnˈsɒlvənt/

insolvent

Meaning
unable to pay debts owed
Example
The insolvent firm could not meet its financial obligations.
C1 adjective /ɪnˈkɒŋɡruəs/

incongruous

Meaning
Not fitting in with or suitable for the surroundings.
Example
His jokes were incongruous during the serious meeting.
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.
C1 adjective /ˌɪnɔːrˈɡænɪk/

inorganic

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.
C1 verb /ˈɪnkjʊˌbeɪt/

incubate

Meaning
to keep eggs, cells, or organisms at the right conditions for development
Example
The hen will incubate the eggs until they hatch.
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 noun /aɪˈtɪnərɛri/

itinerary

Meaning
A planned route or schedule of a journey or trip.
Example
The travel agent gave us a detailed itinerary for our vacation.
C1 adjective /ɪnˈdʌktɪv/

inductive

Meaning
characterized by the inference of general laws from particular instances; reasoning from specific cases to general principles
Example
The scientist used inductive reasoning to form a hypothesis.
C1 adjective /ˈɪmpjəd(ə)nt/

impudent

Meaning
not showing due respect for another person; rude
Example
The impudent child talked back to the teacher.
C1 noun /ˈɪmɪnəns/

imminence

Meaning
the state of being about to happen
Example
The imminence of the storm forced people to take shelter.
C1 noun ˌɪndɪˈspensəbl̩ ˈkɒmpɪtənsi

indispensable competency

Meaning
Essential skill or ability that cannot be done without; a crucial capability that is absolutely necessary.
Example
Digital literacy is an indispensable competency in the 21st century.
C1 noun /ɪnˈsek.tɪ.saɪd/

Insecticide

Meaning
a substance used for killing insects; a chemical pesticide that targets insects
Example
The farmer sprayed insecticide on his crops to protect them from harmful bugs.
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 /ɪnˈdʌstriəs/

industrious

Meaning
Hardworking and diligent in one's duties.
Example
She is an industrious student who always completes her assignments on time.
C1 adjective ɪnˈdel.ə.bəl

indelible

Meaning
Making marks that cannot be removed; impossible to forget or remove.
Example
Her speech left an indelible mark on the audience.
C1 adjective /ˈɪnsjələr/

insular

Meaning
Narrow-minded, isolated, or relating to an island.
Example
The community was criticized for its insular attitudes toward outsiders.
C1 verb /ɪmˈpɜːrsəneɪt/

impersonate

Meaning
to pretend to be another person in order to entertain or deceive
Example
He was arrested for trying to impersonate a police officer.
C1 verb /ɪnˈfleɪt/

inflate

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.
C1 verb /ˌɪn.tɚˈtwaɪn/

intertwine

Meaning
To connect or link closely; to twist together or combine closely.
Example
Their lives became intertwined through years of friendship.
C1 adjective /ˌaɪdiəˈlɪstɪk/

Idealistic

Meaning
pursuing high principles or ideals; unrealistically optimistic
Example
She has an idealistic view of changing the world.
C1 adjective /ɪˈnuːmərəbəl/

Innumerable

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.
C1 adjective ˈɪn.tər.ɪm

interim

Meaning
In or for the intervening period; provisional or temporary.
Example
Interim governments manage transitional phases.
C1 noun /ɪnˈkɜːrʒən/

incursion

Meaning
A sudden attack or invasion into a place or territory.
Example
The army repelled the enemy incursion at the border.
C1 noun /ˈaɪsətəʊp/

isotope

Meaning
Atoms of the same element with equal number of protons but different numbers of neutrons.
Example
Carbon-14 is a radioactive isotope used in dating fossils.
C1 adjective /ɪnˈhɛrənt/

inherent

Meaning
Existing in something as a natural, permanent, or essential quality.
Example
There are inherent risks in extreme sports.
C1 noun /ˈɪn.tə.mə.si/

Intimacy

Meaning
close familiarity or friendship; closeness; a private cozy atmosphere
Example
The couple valued the emotional intimacy they shared more than material possessions.
C1 adjective /ɪˈlʌstriəs/

illustrious

Meaning
Well known, respected, and admired for past achievements.
Example
She had an illustrious career in medicine.
C1 adjective ɪnˈkʌm.bənt

incumbent

Meaning
necessary for (someone) as a duty or responsibility.
Example
It is incumbent upon all citizens to obey the law.
C1 adjective, noun /ˈɪnvəlɪd/ (adjective), /ɪnˈvælɪd/ (noun)

invalid

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.
C1 adjective /ɪnˈvɛntɪv/

inventive

Meaning
Having the ability to create or design new things or to think originally.
Example
The inventor was known for his inventive solutions to everyday problems.
C1 adjective /ˌɪndɪˈvɪzəbl/

indivisible

Meaning
Not able to be divided or separated.
Example
The country's unity was indivisible despite differences.
C1 noun /ˈɪmɪdʒəri/

imagery

Meaning
visually descriptive or figurative language, especially in a literary work
Example
The poet's use of imagery brought the scene to life.
C1 adjective /ɪˈnɔːrdənət/

inordinate

Meaning
Excessive or unusually large in degree.
Example
She spent an inordinate amount of time on her phone.
C1 adjective /ˌɪrɪˈvɜːrsəbl/

irreversible

Meaning
Not able to be undone, changed, or reversed.
Example
The damage caused by the fire was irreversible.
C1 adjective /ˈɪnfəməs/

infamous

Meaning
well known for some bad quality or deed
Example
The dictator was infamous for his cruelty.
C1 noun ˌɪn.fɪlˈtreɪ.ʃən

infiltration

Meaning
The process of entering or gaining access to an organization or place surreptitiously.
Example
Cybersecurity prevents infiltration into sensitive data.
C1 adjective /ˈɪndɪɡoʊ bluː/

Indigo-blue

Meaning
a deep blue color with a purplish tinge
Example
The indigo-blue sky looked magnificent at twilight.
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.
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.
C1 verb /ɪnˈvɜːrt/

invert

Meaning
To turn something upside down or in the opposite position, order, or direction.
Example
He inverted the glass to let the water drain out.
C1 adjective /ˈɪntrɪkət/

intricate

Meaning
very detailed, complex, and difficult to understand
Example
The artist created an intricate pattern on the wall.
C1 adjective /ˌɪnɪkˈskjuːzəbl/

inexcusable

Meaning
Too bad to be justified or overlooked; unforgivable.
Example
His rude behavior was inexcusable.
C1 adjective /ˌaɪ.di.əˈlɒdʒ.ɪ.kəl/

ideological

Meaning
Relating to or based on a system of ideas or beliefs.
Example
The two parties are divided by deep ideological differences.
C1 noun ˌɪnsjʊˈleɪʃən

insulation

Meaning
Material used to prevent heat, sound, or electricity from being transmitted from one area to another.
Example
Insulation of food storage areas can prevent pests from entering.
C1 adjective /ˌɪlɪˈdʒɪtɪmət/

illegitimate

Meaning
Not authorized by law, rules, or standards; not recognized as valid.
Example
The court ruled the contract to be illegitimate.
C1 noun ˌɪnfɛsˈteɪʃən

infestation

Meaning
The presence of an unusually large number of insects or animals in a place, causing damage or disease.
Example
The infestation of ants in the kitchen led to immediate pest control measures.
C1 adjective /ˌɪndɪˈsaɪsɪv/

Indecisive

Meaning
unable to make decisions quickly; hesitant; wavering
Example
She was indecisive about which university to attend.
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 ɪˈluː.sər.i

illusory

Meaning
Based on illusion; not real although seeming to be.
Example
His sense of security was entirely illusory.
C1 verb /ˌɪn.trəˈspekt/

introspect

Meaning
To examine one's own thoughts, feelings, or mental state.
Example
He often introspects before making important decisions.
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.
C1 adjective /ˌɪndɪˈskraɪbəbəl/

Indescribable

Meaning
impossible to describe or express in words; beyond description
Example
The beauty of the sunset was indescribable.
C1 adjective /ˌɪnsərˈmaʊntəbl/

insurmountable

Meaning
Too great to be overcome.
Example
The explorers faced insurmountable odds in the desert.
C1 noun /ˌɪnsɪɡˈnɪfɪkəns/

insignificance

Meaning
The quality of being unimportant or trivial.
Example
He felt a sense of insignificance in the vast universe.
C1 noun /ɪˈreləvəns/

irrelevance

Meaning
the quality of not being connected to or important for a particular matter; lack of significance
Example
His long explanation only highlighted the irrelevance of the details to the main issue.
C1 verb /ɪnˈtruːd/

intrude

Meaning
To enter a place or situation where one is not wanted or not invited.
Example
He felt embarrassed to intrude on their private conversation.
C1 adjective /ˌɪnsɪˈdɛntəl/

incidental

Meaning
happening as a minor part or in connection with something else
Example
Incidental expenses like snacks and tips were included in the bill.
C1 noun /ɪˈnɜː.ʃə/

Inertia

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.
C1 verb /ˈɪnstɪˌɡeɪt/

instigate

Meaning
To bring about or initiate an action, often something negative.
Example
He was accused of instigating the riot.
C1 adjective ˈɪn.lənd

Inland

Meaning
Situated in the interior of a country; away from the coast.
Example
Inland transport boosts local trade.
C1 adjective /ˌɪrɪˈspɛktɪv/

Irrespective

Meaning
without taking something into account; regardless of
Example
All students will be treated equally, irrespective of their background.
C1 adjective /ˌɪrɪˈprɛsəbl̩/

irrepressible

Meaning
Impossible to control or restrain.
Example
She had an irrepressible urge to laugh during the speech.
C1 adjective /ɪnˈfɜːm/

infirm

Meaning
Weak, especially due to old age or illness.
Example
The infirm old man needed assistance to walk.
C1 adjective ˌɪn.təˈdɪs.ɪ.plɪ.nər.i

interdisciplinary

Meaning
Relating to more than one branch of knowledge.
Example
The interdisciplinary approach in education enhances problem-solving skills.
C1 verb /ˈɪmplɪˌkeɪt/

implicate

Meaning
To show someone’s involvement in a crime or wrongdoing.
Example
The evidence implicated several officials in the scandal.
C1 adjective /ɪmˈpjʊər/

Impure

Meaning
contaminated; not clean; mixed with foreign substances
Example
The impure water caused health problems in the village.
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 adverb /ˌɪn.dɪˈskrɪm.ɪ.nət.li/

Indiscriminately

Meaning
without making careful distinctions; randomly; without discrimination
Example
The company fired employees indiscriminately without considering their performance.
C1 adjective /ɪnˈtændʒəbl/

intangible

Meaning
Unable to be touched or grasped; not having a physical presence.
Example
Trust is an intangible quality in relationships.
C1 adjective /ɪnˈtɛlɪdʒəbl/

intelligible

Meaning
Able to be understood; clear enough to be comprehended.
Example
Her speech was barely intelligible over the noise.
C1 adjective /ˈɜːrksəm/

irksome

Meaning
annoying or irritating
Example
Waiting in a long line is one of the most irksome tasks.
C1 adjective /ˌɪnkɒmprɪˈhɛnsəbl/

incomprehensible

Meaning
Impossible or very difficult to understand.
Example
The professor’s lecture was so fast it became incomprehensible.
C1 noun /ɪnˈɛk.wɪ.ti/

inequity

Meaning
Lack of fairness or justice; unequal distribution or treatment.
Example
Social inequity continues to be a global issue.
C1 noun ˌɪn.tuˈɪʃ.ən

intuition

Meaning
The ability to understand something immediately, without the need for conscious reasoning.
Example
Her intuition told her something was wrong.
C1 adjective ˌɪdiəsɪnˈkrætɪk

idiosyncratic

Meaning
Relating to idiosyncrasy; peculiar or individual.
Example
His idiosyncratic behavior set him apart from his colleagues.
C1 noun /ˌɪntɪˈmeɪʃən/

intimation

Meaning
A subtle or indirect hint or suggestion.
Example
She gave no intimation of her plans.
C1 adjective ˌɪn.təˈstel.ər

interstellar

Meaning
Occurring or situated between stars.
Example
Scientists study interstellar travel possibilities.
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 /ɪmˈpɜːrtɪnəns/

impertinence

Meaning
lack of respect; rudeness
Example
The teacher was shocked by the student's impertinence.
C1 adverb /ɪnˈdɛfɪnətli/

indefinitely

Meaning
for an unlimited or unspecified period of time
Example
The project has been postponed indefinitely.
C1 adjective, noun /ɪnˈdɪkətɪv/

indicative

Meaning
Serving as a sign or expression of something; in grammar, a mood used to make factual statements.
Example
His tone was indicative of his frustration.
C1 noun /ɪnˈsɜːʃən/

insertion

Meaning
the action of inserting something into something else
Example
The insertion of the new data was completed successfully.
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.
C1 adjective /ɪnˈtræk.tə.bəl/

intractable

Meaning
Difficult or impossible to manage, control, or solve.
Example
The conflict has become an intractable problem.
C1 adjective /ˌɪndɪˈskriːt/

indiscreet

Meaning
Not careful in what one says or does, likely to reveal secrets or offend.
Example
It was indiscreet of him to mention the plan in public.
C1 noun /aɪˈdiː.ə.lɪ.zəm/

Idealism

Meaning
the pursuit of high principles and noble goals; unrealistic pursuit of perfection
Example
His youthful idealism motivated him to join various social justice movements.
C1 adjective /ɪˈledʒ.ə.bəl/

illegible

Meaning
Not clear enough to be read; unreadable.
Example
The doctor’s handwriting was almost illegible.
C1 adjective /ɪˈmækjələt/

immaculate

Meaning
perfectly clean, neat, or free from flaws
Example
Her room was immaculate, with everything in its place.
C1 adjective /ɪnˈstrʌktɪv/

instructive

Meaning
useful and informative; providing knowledge or instruction
Example
The lecture was highly instructive and engaging.
C1 adjective /ɪnˈhjuːmən/

Inhuman

Meaning
lacking human qualities; cruel; brutal; savage
Example
The dictator's inhuman treatment of prisoners shocked the international community.
C1 verb /ɪnˈfrɪndʒ/

infringe

Meaning
To actively break the terms of a law, agreement, or right.
Example
Copying this software without permission will infringe copyright laws.
C1 adjective /ɪˈnɛpt/

inept

Meaning
lacking skill or ability; clumsy or incompetent
Example
His inept handling of the situation made it worse.
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.
C1 adjective /ɪmˈpoʊzɪŋ/

imposing

Meaning
having an appearance that is grand, impressive, or commanding
Example
The castle is an imposing structure overlooking the valley.
C1 verb /ɪmˈpɛər/

impair

Meaning
to weaken or damage something, especially a function or ability
Example
Smoking can impair your lung capacity.
C1 adjective /ɪˈrɛpərəbəl/

Irreparable

Meaning
impossible to repair or fix; permanent damage that cannot be undone
Example
The accident caused irreparable damage to his spine.
C1 adjective /ɪˈmeʒərəbəl/

Immeasurable

Meaning
too large or extensive to measure; boundless
Example
The immeasurable love of a mother knows no bounds.
C1 adjective /ɪnˈdiːsənt/

indecent

Meaning
not conforming to accepted standards of behavior or morality; improper or offensive
Example
He was warned for making an indecent remark during the meeting.
C1 adjective /ˌɪn.səˈbɔːr.dɪ.nət/

insubordinate

Meaning
Defiant of authority; disobedient to orders.
Example
The insubordinate employee refused to follow the manager's instructions.
C1 adjective /ɪnˈvɪnsəbl/

invincible

Meaning
too powerful to be defeated or overcome
Example
The team seemed invincible after winning ten matches in a row.
C1 noun /ˌɪn.dʒəˈnjuː.ɪ.ti/

ingenuity

Meaning
The quality of being clever, original, and inventive.
Example
His ingenuity led to groundbreaking innovations.