103 Adjectives That Start With “I”

“I” is an all-important letter. On its own, it’s the word for self-expression, but it’s also the beginning to some incredible adjectives. An intriguing prospect, right? The nearly infinite array of adjectives that start with “I” gives you an inexhaustible source of inspiring words to play with and include in your increasing vocabulary.

It never hurts to look on the brighter side of life. Having some positive adjectives that start with “I” in your back pocket ensures that you have the perfect words to describe your inimitable friends, industrious coworkers, and incomparable family members.

Adjective	Definition	Synonyms
idiosyncratic	distinctive; particular; individual	unique, quirky, distinct
idyllic	peaceful, tranquil, or pretty	pleasant, pastoral, unspoiled
illustrious	well-known and respected	distinguished, eminent, transcendent
imaginative	having or showing creativeness or resourcefulness	clever, fanciful, inventive
immaculate	spotless; no stains	flawless, perfect, pure
impactful	having a significant or powerful effect	impressive, poignant, stunning
impeccable	the highest standards of propriety; flawless	perfect, spotless, unblemished
important	having great significance or consequence	eminent, influential, outstanding
impressive	leaving a feeling of awe or admiration	moving, inspiring, telling
incomparable	having no common basis for comparison	excellent, superior, unparalleled
incredible	impossible to believe	unbelievable, wonderful, amazing
indefatigable	having tireless persistence	diligent, dogged, unrelenting
industrious	hard-working	ambitious, assiduous, productive
ineffable	too great for words	indescribable, inexpressible, transcendent
infallible	incapable of mistakes or errors	flawless, perfect, unerring
ingenious	clever, talented, possessed of genius	smart, bright, resourceful
inimitable	impossible to copy or imitate	unique, matchless, distinct
innocent	free from sin	blameless, spotless, upright
insightful	showing a deep understanding	astute, discerning, perceptive
inspiring	encouraging someone	motivating, encouraging, influential
intelligent	clever; a high level of intelligence	smart, bright, sharp
interesting	arousing curiosity or interest	fascinating, compelling, intriguing
intrepid	unafraid; fearless	brave, courageous, bold
intriguing	arousing curiosity or interest	interesting, engaging, riveting
intoxicating	causing great happiness	exciting, exhilarating, invigorating
invigorating	filling one with energy or strength	energizing, refreshing, revitalizing
inviting	alluring, making itself wanted or desired	tempting, welcoming, attractive

At the same time, some moments or people call for more of a negative approach. While you shouldn’t always be an Icy Ivan, some people are just improper and can leave you feeling irate and irritated.

Adjective	Definition	Synonyms
icky	gross; sticky	gooey, vile, displeasing
icy	very cold or, in dealing with people, unfriendly; hostile	aloof, unwelcoming, inhospitable
idealistic	unrealistically aiming for perfection	unrealistic, impractical, lofty
idiotic	incredibly stupid	silly, mindless, witless
illegitimate	not authorized by law	unlawful, illegal, criminal
illicit	forbidden by law or customs; against the law	illegal, outlawed, prohibited
illogical	lacking sense or reason	unreasonable, irrational, nonsensical
immoral	not conforming to the standards of morality	unethical, unscrupulous, disreputable
impassable	impossible to pass or travel through	impenetrable, obstructed, untraversible
impetuous	acting impulsively	impulsive, reckless, foolhardy
impish	inclined to do naughty things for fun	mischievous, devilish, roguish
improper	not in accordance with the rules	inappropriate, unseemly, unbecoming
inapt	unsuitable; unfitting	unfitting, unsuitable, unprofessional
incompetent	lacking the skills to accomplish something	bungling, unskillful, unprofessional
inept	showing no skill	clumsy, unskillful, feckless
inferior	of a lower quality	lesser, substandard, low-quality
infernal	relating to hell; the underworld	hellish, subterranean, chthonic
inglorious	shameful; loss of honor; disgraceful	shameful, dishonorable, disgraceful
insipid	lacking flavor; not exciting or interesting	bland, boring, dull
intransigent	uncompromising; unwilling to see other's views; inflexible	unyielding, uncompromising, stubborn
irascible	easily angered; irritable	quick-tempered, short-tempered, crabby
irate	extremely mad	angry, furious, enraged
irreconcilable	points of view that are so different, they cannot be made compatible	incompatible, incongruous, discordant
irrelevant	beside the point; not important	tangential, extraneous, unimportant
irritable	having a tendency to be easily angry or annoyed	bad-tempered, touchy, grumpy

Sometimes, you just need a good, middle-of-the-road word to describe your situation. Maybe you’re inside, looking for the perfect indigo shirt, feeling a bit introverted, or want to learn about Indigenous people.

Adjective	Definition	Synonyms
iconoclastic	attacking beliefs or hierarchies; nonconformist	individualistic, nonconformist, critical
illusive	dreamlike; not based in reality	deceptive, imaginary, false
impermeable	does not allow liquid to pass through; insusceptible	airtight, hermetic, sealed
improbable	not likely to happen	impossible, unbelievable, doubtful
immune	protected or exempt; resistant to infection	unaffected, resistant, exempt
inadvertent	not happening through planning	unintentional, unwitting, accidental
inanimate	not alive; lifeless	inert, lifeless, motionless
inclined	leaning away from horizontal or vertical; having a preference	slanted, biased, sloping
inconceivable	not capable of being grasped	unbelievable, extraordinary, mind-boggling
inconspicuous	not easily noticed or visible	concealed, camouflaged, hidden
indicative	suggestive; serving as a sign	suggestive, emblematic, symbolic
indigenous	native to a particular place	endemic, innate, original
indigo	dark blue in color	blue-green, azure, cerulean
intended	planned or meant on purpose	expected, calculated, predetermined
intensive	thorough; concentrated on a specific area	comprehensive, thorough, in-depth
intrinsic	essential; inherent	elemental, underlying, built-in
inside	interior; inner	indoors, internal, central
instant	happening immediately	prompt, on-the-spot, swift
integral	necessary; essential	fundamental, vital, indispensable
intense	possessing extreme force or fierce strength	fierce, great, extreme
intricate	containing a lot of complex parts	complicated, detailed, elaborate
introverted	having a personality that is shy or more preoccupied with oneself	shy, reserved, withdrawn
invincible	unconquerable; indestructible	invulnerable, indestructible, unbeatable
ironic	occurring in a way that is the opposite of what was expected	sardonic, sarcastic, satirical
irrevocable	irreversible; not able to change	permanent, unchangeable, fixed
itty-bitty	tiny	small, diminutive, minuscule

The world of adjectives that start with “I” is imbued with an infinite array of fun words. Whether you need to describe something that’s fishlike (ichthyic) or find the right fire-adjacent word (igneous or inflammable), the letter “I” has you covered.

Adjective	Definition	Synonyms
ichorous	relating to any acrid, watery fluid	melted, aqueous, dissolved
ichthyic	fishlike	piscine, fishy
idiomatic	related to a particular language or dialect; having a distinct style	dialectal, colloquial, vernacular
idiopathic	occurring spontaneously or without known cause, typically of a disease	spontaneous, unexplained, unidentified
igneous	of or relating to fire; (in geology) produced under processes involving intense heat	burning, molten, roasting
illaudable	unworthy of praise	shameful, unworthy, disreputable
imbricate	overlapping in sequence; resembling overlapping tiles	overlapping, covered, enveloped
impecunious	having little money	penniless, poor, destitute
impromptu	without planning or forethought	improvised, unscripted, spur-of-the-moment
imprudent	unwise; without thought of consequences	reckless, rash, careless
impudent	disrespectful or offensively bold	rude, disdainful, brazen
impugnable	open to question or debate	debatable, doubtful, precarious
inauspicious	unfavorable, not of good omen	unfortunate, baleful, ominous
inceptive	related to the beginning of something	nascent, earliest, foremost
incredulous	of a person unable or unwilling to believe	unbelieving, skeptical, unconvinced
incognito	having your identity concealed	disguised, concealed, anonymous
incorrigible	beyond correction; firmly fixed; not easily changed	stubborn, uncorrectable, incurable
incumbent	necessary as an obligation or duty	binding, compelling, urgent
infinitesimal	extremely small	microscopic, minuscule, tiny
inflammable	easily set on fire	flammable, incendiary, combustible
innoxious	harmless	nontoxic, safe, bland
invertebrate	without a backbone; having no strength of character	spineless, ineffective, inefficacious
iridescent	shining with numerous colors like a rainbow	lustrous, shimmering, opalescent
ironclad	protected in iron; impossible to change or contradict	inflexible, unwavering, firm
itinerant	traveling from place to place	wandering, roving, migratory

You saw the words, but seeing them in action can help you understand how inviting or irrelevant they might be.

Stop that infernal racket!
The book we bought our host was an incredible Irish cookbook.
His dining room was painted a deep shade of indigo that made the place seem fit for a king.
When we looked around his house, we realized that his taste was impeccable.
She was an undeniably beautiful girl, but her intelligent air made her even more attractive.
When we arrived very late, our host was so irate he made us find another place to stay.
The waiter's icy manner didn't sit well with the customers.
That icky new candy bar isn't selling well.
The invincible defense of the football team took them all the way to the playoffs.
Her impactful speech made me rethink everything about my life.
The teacher’s insightful analysis helped the class understand the books’ themes.
It felt great to escape the loud, busy city and enjoy the quiet, idyllic countryside, even if it only lasted one week.
The professor’s insipid lecture put most of the class to sleep.
Even though he’s really talkative around his friends, he tends to be more introverted around strangers.
Our truly indefatigable friend spent her weekend babysitting her niece, running a marathon, and hosting a party, all without needing to rest.
I was tired and exhausted in the morning, but an invigorating lunch with my friend was all I needed to keep going.
The toy has a lot of intricate pieces, so please be careful when handling it.
No one seemed willing to talk at dinner, so she gave an impromptu speech about her vacation.
His quiet demeanor and lack of participation was indicative of a bad morning.
Even though his attempt at making dinner was an irrevocable failure, he knew what he did wrong, so he could do better next time.

Indeed, now you have intensive knowledge of adjectives that start with “I,” but don’t stop there. Learning other words that start with “I” is a great way to improve your overall reading and writing abilities.

103 Adjectives That Start With “I”

Positive Adjectives That Start With “I”

Negative Adjectives That Start With “I”

Neutral Adjectives That Start With “I”

Fun and Uncommon Adjectives That Start With “I”

Example Sentences for Adjectives That Start With “I”

Other “I” Words for Your Eyes