The equilibrium length of this spring is 5 centimeters.

He prefers natural foods.

Calculating the natural logarithm is an important part of mathematics.

His car spontaneously combusted all of a sudden.

This wood may spontaneously combust if the humidity is high.

Natural rights are rights that humans have from birth.

We must strive to protect the natural environment.

He is known as the supreme leader of that country.

Among my family, I am the tallest.

I am busy with work during the day.