The theory of harmonic oscillators is a fundamental concept in physics.

She's always a goody two shoes, and is well-liked by her teachers.

Yuriko is my best friend.

We are aiming to kill two birds with one stone with this plan.

The Atlantic puffin is one of the most commonly seen birds in the North Atlantic.

He was considered the wisest among the ignorant, like a bat in the land of the blind.

The Papua fire-eating bird, with its unique appearance, is a bird you won't forget once you see it.

She said 'to each his own', respecting the differences among people.

A binary operator is one of the basic concepts in algebra.

The Chinese white dolphin lives in the waters off the southern coast of China.