na-adjective, noun
Formal term used mainly in medical, biological, or technical writing to describe organisms or cells that are not yet fully developed. Not used in everyday conversation about children.
幼若な細胞はまだ分化していない。
Juvenile cells have not yet differentiated.
この動物の幼若個体は親とは色が異なる。
The juvenile individuals of this animal differ in color from the adults.