ruga (noun)

1. In the comic book, the artist drew detailed rugae on the superhero's forehead to show his concentration.

2. The painter skillfully depicted the rugae on the subject's face, showcasing the realistic details in the portrait.

3. In the futuristic world of the science fiction novel, humans have developed synthetic skin that mimics the natural rugae patterns.

4. As the anime character expressed surprise, her forehead rugae deepened, emphasizing her emotions.