immature

American  

[im-uh-choor, -toor, -tyoor, -chur] / ˈɪm əˈtʃʊər, -ˈtʊər, -ˈtjʊər, -ˈtʃɜr /

adjective

1. not mature, ripe, developed, perfected, etc.

2. emotionally undeveloped; juvenile; childish.

   Synonyms:

   babyish, puerile, callow

3. Physical Geography. youthful.

4. Archaic. premature.

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immature British  

/ -ˈtʃʊə, ˌɪməˈtjʊə /

adjective

1. not fully grown or developed

2. deficient in maturity; lacking wisdom, insight, emotional stability, etc

3. geography a less common term for youthful

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Other Word Forms

• immatureness
  noun
• immaturity
  noun
• immaturely
  adverb

Etymology

Origin of immature

First recorded in 1540–50, immature is from the Latin word immātūrus unripe, hence, untimely. See im- ², mature

Explanation

Use the adjective immature to describe something that is not fully grown: “Elizabeth rescued an immature sparrow that had fallen from its nest during the storm.” When used in a general sense, immature describes something in an early stage of development, such as an immature fruit tree or an immature political system. When applied to people, however, immature is often used to describe someone who behaves in a childish way. So if your 42-year-old brother spends the entire holiday weekend playing video games and then throws a temper tantrum when you ask him to help with the dishes, the word you’re looking for to describe him is probably immature.

Related Words

• childish
• premature