immature

adjective

im·​ma·​ture ˌi-mə-ˈchu̇r  -ˈtu̇r 

-ˈtyu̇r

1

a

: exhibiting less than an expected degree of maturity

emotionally immature adults

b

: lacking complete growth, differentiation, or development

immature fruits

a sexually immature bird

c

: having the potential capacity to attain a definitive form or state : crude, unfinished

a vigorous but immature school of art

2

archaic : premature

immature noun

immaturely adverb

immaturity

ˌi-mə-ˈchu̇r-ə-tē 

-ˈtu̇r-

-ˈtyu̇r-

noun

Synonyms

• young
• juvenile

Examples of immature in a Sentence

The flock included both adult and immature birds.

His teachers have complained about his immature behavior.

Recent Examples on the Web

After hatching, the immature cicadas or nymphs spend 17 or 13 years underground, feeding on roots, then emerge during the spring and transform into adult cicadas. —Saleen Martin, USA Today, 14 June 2025

And babies younger than six months old—who are ineligible for vaccination because of their immature immune system—have the highest rates COVID hospitalization after adults aged 75 and older. —Lauren J. Young, Scientific American, 10 June 2025

Swit’s Houlihan was a tough-as-nails nurse who did things by the book and disapproved of the immature antics displayed by the likes of Alan Alda’s Hawkeye. —Dave Nemetz, TVLine, 30 May 2025

But the researchers note that adult howlers are nearly three times the weight of immature capuchins, so a would-be kidnapper might face serious risks. —Nell Greenfieldboyce, NPR, 19 May 2025

Word History

Etymology

Latin immaturus, from in- + maturus mature

First Known Use

1548, in the meaning defined at sense 2

Rhymes for immature

• annexure
• embouchure
• epicure
• paramour
• premature
• reassure
• reinsure
• sinecure
• abjure
• adjure
• allure
• assure

Kids Definition

immature

adjective

im·​ma·​ture ˌim-ə-ˈt(y)u̇(ə)r 

1

: not mature or fully developed : young, unripe

an immature bird

immature fruit

2

: showing less than an expected degree of maturity

immature behavior

immaturely adverb

Medical Definition

immature

adjective

im·​ma·​ture

ˌim-ə-ˈt(y)u̇(ə)r also -ˈchu̇(ə)r

: lacking complete growth, differentiation, or development

immature blood cells

emotionally immature

immaturely adverb

immaturity

-ˈt(y)u̇r-ət-ē also -ˈchu̇r-

noun

plural immaturities