His true value is his leadership under difficult circumstances.

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

I saw an old man playing with his grandson in the park.

He has contributed to the company for many years as an elderly worker.

Let's respect the elderly and learn from their knowledge.

The old man takes a walk in the park every day.

An old person was playing with his grandson in the park.

Recently, my mother's presbyopia has been progressing, making it difficult for her to read.

My old dog is still energetic.

Our body is constantly excreting waste products.