GRAMMAR DETAIL

〜びる

to take on the air of

Indicates that the outward appearance of a particular status or mature manner, such as that of an adult, has become evident.

Examples

まだ若いのに、彼は妙に大人びた話し方をする。

Although he is still young, he speaks in an oddly mature way.

小学生なのに、彼は大人びて見える。

Although he is in elementary school, he looks mature for his age.

久しぶりに会った甥はすっかり大人びていた。

My nephew looked completely grown-up when I saw him for the first time in a while.

Structure: In forms such as 大人びる, びる attaches to certain nouns to describe showing that quality in appearance or manner. 大人びる is read おとなびる.
Basic usage: 小学生なのに、彼は大人びて見える。 means that he looks mature even though he is an elementary school student.

Modifying a noun versus linking to a verb
- 大人びた話し方 uses 大人びた to modify a noun, meaning a mature way of speaking. 大人びて見える links with the て-form to describe the impression of looking mature.