Translation guide
The English word "immature" covers a range of meanings from biological underdevelopment to childish behavior. In Japanese, different words and expressions are used depending on whether you mean physically unripe, emotionally childish, or lacking experience.
Describing a person whose behavior, attitude, or emotional reactions are like a child's, often in a negative sense.
Literally 'unripe', this is the most direct and common translation for 'immature' when referring to a person's character, skills, or emotional development. It can be used in both formal and casual contexts.
He is still emotionally immature.
Get rid of such immature thinking.
Means 'childish' or 'infantile'. It carries a stronger negative connotation than 未熟 and is often used to criticize someone's behavior as puerile or silly.
I'm disgusted by his immature behavior.
Such a childish excuse won't work.
Literally 'lacking adultness', this is used when an adult acts in a way unbecoming of their age. It implies the person should know better.
His reaction was immature.
Let's stop this immature fight.
Means 'childish' or 'like a child'. It can be neutral or negative depending on context, but often implies immaturity in a less harsh way than 幼稚.
She still has some immature traits.
Describing plants, animals, or body parts that are not yet mature or ripe.
The same word as above, but applied to physical immaturity. It can describe unripe fruit, undeveloped organisms, or immature cells.
This fruit is still immature.
Immature cells differentiate.
A more explicit phrase meaning 'not mature'. It is often used in biological or technical contexts.
Literally 'blue/green', but can mean 'unripe' for fruit or 'inexperienced' for people. For physical immaturity, it's mainly used for unripe fruit.
Describing someone who is new to a job, activity, or field and hasn't yet reached full competence.
Describing something abstract like a concept, proposal, or artistic work that is still in an early, unpolished stage.
Once more, 未熟 is versatile enough to cover this meaning. It suggests the idea or work needs further refinement.
The plan is still immature.
It's an immature theory, but interesting.
Means 'under development' or 'developing'. It is often used for fields, technologies, or countries, but can apply to ideas that are not yet mature.
Literally 'incomplete'. It emphasizes that something is not finished, which can be a form of immaturity for creative works.
未熟 (みじゅく) is the most versatile and neutral word for 'immature'. It can be used for people, skills, ideas, and physical immaturity. 幼稚 (ようち) is specifically for childish behavior and carries a negative, critical tone. Use 未熟 when you want to state immaturity as a fact or lack of development; use 幼稚 when you want to call someone's actions puerile.
He is immature, but he is making an effort.
I can't stand his immature (childish) attitude.
The loanword イマチュア (imachua) is rarely used in natural Japanese. It might appear in some contexts like music genres or specific jargon, but it is not a standard translation for 'immature'. Stick to the native Japanese words above.
Stop being so immature!
Using 幼稚 emphasizes the childishness.
His understanding of the topic is still immature.
The fruit is too immature to eat.
This animal is still sexually immature.
青いバナナは食べられない。
You can't eat immature (green) bananas.
Literally 'lack of experience'. This is a more specific way to say someone is immature due to insufficient experience.
His failure is due to immaturity (lack of experience).
Means 'half-fledged' or 'not yet a full-fledged person'. It implies someone is still learning and not yet fully capable. Often used humbly about oneself.
I'm still an immature (half-fledged) craftsman.
This field is still immature (developing).
その小説はまだ未完成だ。
The novel is still immature (unfinished).