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Adults

Adults are people or animals that have reached full maturity.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 27, 2026|2 min read| Fact-checked

Adults are people or animals that have reached full maturity. In humans, the term usually refers to someone who has reached the legal age of majority, often 18, though this varies by jurisdiction. The word is also used more broadly for mature, fully developed organisms and for content intended for mature audiences.

Definition and usage

The term adult is used as both a noun and an adjective. It commonly refers to a fully developed person or organism, and can also mean something suitable for grown people.

For humans, adulthood is often defined by the age of majority, when a person is legally responsible for their actions. The exact age depends on the jurisdiction.

Biological adulthood

In biology, adulthood begins when an organism reaches sexual maturity. This usage applies to humans, animals, and sometimes plants.

Adult as a media label

In publishing and entertainment, adult can describe content intended for mature audiences. This often includes sexual material and content not intended for children.

Adulthood in Canada

In Canada, adulthood is commonly associated with the age of majority, which is determined by provincial and territorial law and is not the same everywhere.

Key facts

  • In general English, an adult is someone or something that is fully grown or mature.
  • In law, adulthood usually begins at the age of majority, which varies by country and sometimes by state or province.
  • In biology, an adult organism has reached sexual maturity and can reproduce.
  • The word can also describe material intended for mature audiences, including sexually explicit content.
  • The term is used for humans, animals, and sometimes plants.
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Canadian context

In Canada, adulthood is commonly associated with the age of majority, which is determined by provincial and territorial law and is not the same everywhere.

Frequently asked questions

What is an adult?
An adult is a fully grown or mature person or organism.
At what age is someone usually considered an adult?
In many countries, adulthood begins at 18, but the legal age of majority varies by jurisdiction.
What does adult mean in biology?
In biology, an adult is an organism that has reached sexual maturity and can reproduce.
Can adult refer to animals?
Yes. It can refer to a fully grown animal as well as a human being.
What does adult mean on media labels?
It usually means the material is intended for mature audiences and may contain explicit sexual content.

References

  1. Merriam-Webster — https://www.merriam-webster.com/dictionary/adult
    Supports: Definitions of adult as fully developed, relating to adults, and dealing in explicitly sexual material
  2. Cambridge Dictionary — https://dictionary.cambridge.org/us/dictionary/english/adult
    Supports: Adult as a fully grown person or animal; age of 18 in English law; adult content meaning
  3. Cornell Law School Legal Information Institute — https://www.law.cornell.edu/wex/adult
    Supports: Legal definition of adulthood as reaching the age of majority and variation by jurisdiction
  4. Wikipedia — https://en.wikipedia.org/wiki/Adult
    Supports: Biological adulthood as sexual maturity and general discussion of legal and social meanings
  5. PubMed Central — https://pmc.ncbi.nlm.nih.gov/articles/PMC5382900/
    Supports: WHO-related definition of adulthood and distinction from adolescence