What does grownup mean?
“Grownup” is an informal word for an adult or for behavior that is supposed to be mature, sensible, and responsible. As a noun, it names a person who has reached adulthood; as an adjective, it describes conduct, decisions, or responsibilities considered appropriate to an adult. The word is especially common in speech involving children, and it can sound affectionate, mildly patronizing, or playfully nostalgic depending on context. Closely related forms include the more standard hyphenated adjective and noun “grown-up” and the verb phrase “grow up,” which refers to the process of becoming an adult. “Grownup” is useful because it carries both a straightforward meaning and a social one: it names age and maturity while reminding us that ideas about adulthood are often learned, negotiated, and expressed in familiar language. In everyday English, it usually appears in family, school, and conversational contexts rather than formal writing.
An adult person, especially when the speaker is addressing or referring to children.
"The grownups stayed up talking after the children had gone to bed."
Informal and often affectionate; the more standard hyphenated form is “grown-up.”
Mature, sensible, or appropriate in the behavior or judgment of an adult.
"They made the grownup decision to postpone the trip."
Common in informal speech and often mildly ironic when applied to immature behavior.
The plural is commonly written as one word in British informal usage; “grown-ups” is the standard hyphenated form used in both British and US English.
"The grownups discussed the problem while the children played outside."
“Grownup” sounds like a noun, an adjective, and a childhood challenge all at once.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does grownup come from?
“Grownup” is a compound of “grow” and “up,” both long-established English words. The expression developed in 19th-century English for a person who had reached adulthood and, by extension, for behavior regarded as mature.
Related word forms
How grownup is actually used
The word is informal and especially associated with speech involving children. It can be affectionate or mildly patronizing. The closed form is particularly common in British informal usage, while the hyphenated “grown-up” is standard in both British and US English and is the more common US form.
Easily confused with grownup
“Grown-up” is the standard hyphenated adjective and noun, while “grownup” is a common unhyphenated informal form.