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

Sometimes, homeowners are accommodating adult children who still live with them or are making room for their own elderly parents.

From The Wall Street Journal ● Jul. 17, 2026

Meyering carefully threads the themes of parental concern and young adult independence throughout her screenplay.

From Los Angeles Times ● Jul. 16, 2026

Monday's expert report also recommended restricting social media for children under the age of 13, with access only allowed under adult supervision.

From Barron's ● Jul. 14, 2026

In years gone by, most people would get a bank account early in their adult life and stick with it for decades.

From BBC ● Jul. 12, 2026

“You can’t give an adult permission for anything.”

From "Boy 2.0" by Tracey Baptiste

She said the lack of alleys and limited places to cross the street already make it difficult for customers to reach her business, particularly older adults and people with disabilities who need to park nearby.

From Los Angeles Times ● Jul. 17, 2026

TikTok began closing the gap in 2024, when US adults were spending nearly as much time on the app as on Netflix, according to eMarketer data.

From Barron's ● Jul. 16, 2026

The streamer has notched hit after hit by tapping in to the fervent, rapidly growing audience of young adults hungry for coming-of-age love stories.

From The Wall Street Journal ● Jul. 15, 2026

While adults age 40 and older overwhelmingly believe healthy behaviors support brain health, many do not practice them consistently.

From MarketWatch ● Jul. 15, 2026

The adults sit at the table and us kids find spots in the grass to stretch our legs.

From "Clairboyance" by Kristiana Kahakauwila

Related Words

• man
• person
• woman