adult

American  

[uh-duhlt, ad-uhlt] / əˈdʌlt, ˈæd ʌlt /

noun

• adults
  plural

1. a person who is fully grown or developed or of age.

2. a full-grown animal or plant.

3. a person who has attained the age of maturity as specified by law.

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adjective

1. having attained full size and strength; grown up; mature.

   an adult person, animal, or plant.

2. of, relating to, or befitting adults.

3. intended for adults; not suitable for children.

   adult entertainment.

verb (used without object)

1. Informal. (of a young person) to do things and assume responsibilities that are associated with being an adult; act like an adult (usually used facetiously about minor accomplishments).

   I cook dinner for myself most nights—guess that means I'm adulting.

adult British  

/ ˈædʌlt, əˈdʌlt /

adjective

1. having reached maturity; fully developed

2. of or intended for mature people

   adult education

3. regarded as suitable only for adults, because of being pornographic

   adult films and magazines

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noun

1. a person who has attained maturity; a grownup

2. a mature fully grown animal or plant

3. law a person who has attained the age of legal majority (18 years for most purposes) Compare infant

Usage

What does adult mean? An adult is a person who is fully grown or developed. This could refer to a person’s body being done growing or their mind being fully developed. An adult child is someone’s child who is fully grown, as in Murray’s adult children are all married and have children of their own. An adult is also a person who has reached an age that their society says allows them responsibilities and benefits not allowed to children. For example, in the United States someone who is 18 years old is in many cases considered an adult. Eighteen-year-olds can vote, sign a contract, join the military, and other actions children are not allowed to do. An adult can also be a fully grown or matured plant or animal, as in Once my puppy becomes an adult, I’ll need to get them a bigger crate. Adult can also be used to describe something related to adults or adulthood, such as adult responsibilities—like paying rent. Adult can also be used to describe something not suitable for children. Things labeled as adult entertainment, for example, often include explicit sexual content. Informally, adult can be used as a verb meaning to take on responsibilities usually reserved for adults, such as owning a house. It’s often used humorously to describe small responsibilities, as in Tanya really adulted today by putting away her laundry.

Other Word Forms

Derived Forms

• adulthood
  noun
• adultness
  noun
• subadultness
  noun
• adultlike
  adjective
• nonadult
  adjective
• quasi-adult
  adjective
• subadult
  adjective
• unadult
  adjective
• adultly
  adverb

Inflected Forms

Nouns

• adults
  plural

Etymology

Origin of adult

First recorded in 1525–35; from Latin adultus “grown” (past participle of adolēre “to make grow”), equivalent to ad- ad- + ul- (identical with base al- in aliment ( def. ) ) + -tus past participle suffix

Explanation

Adult is noun and an adjective, both of which refer to something mature, no longer a child. A full-grown person is called an adult: they can vote, rent cars, and choose to eat sugary cereal for dinner every night. If you're still a child, then you are not an adult — that's the noun version. Childish people don't behave in an adult manner — that's the adjective. A child might be scared by the Wicked Witch of the West, but an adult knows she's not real. Learning the difference between real life and make-believe is one of the upsides of becoming an adult.

Example Sentences

See Examples For:

adult adults

He said the purpose was to give a young person "some resources for when they became an adult so that it would actually give them a good start".

From BBC ● Aug. 6, 2026

Any interested party — a hospital, nursing home, social worker, adult protective services, friend or relative — can file a formal petition with the local probate or superior court.

From MarketWatch ● Aug. 5, 2026

However, only one of the 15 elephants affected was an adult male.

From BBC ● Aug. 4, 2026

Yet the music reflects an emotional wisdom that had to be earned through experience, as in the folky “Time,” which ponders her and Roach’s relationships with their two adult sons.

From Los Angeles Times ● Aug. 4, 2026

We had run long in a day—a hundred and fifty miles—with an adult team in good shape.

From "Woodsong" by Gary Paulsen

Millions of adults and children across England are facing longer wait times for mental health care, the Guardian says, as more than 66% of NHS providers plan to reduce or shut down service completely.

From BBC ● Aug. 7, 2026

During closing arguments, prosecutor Linda Singer told jurors that Meta's algorithms had directed adults toward content posted by teenage users while the company concealed internal findings about the risks to young people.

From Barron's ● Aug. 7, 2026

Roughly a third of adults now consult AI for health advice, leaving doctors to untangle erroneous guidance.

From The Wall Street Journal ● Aug. 6, 2026

The FDA greenlit mFlusiva for adults age 50 and up, and Moderna wants to have it available for the coming flu season—that is, a few months from now.

From Slate ● Aug. 6, 2026

Over the pouring rain and howling wind, the adults shouted Chicken’s name.

From "Caterpillar Summer" by Gillian McDunn

Related Words

• man
• person
• woman