He is in the third year of junior high school, or in other words, he is in the 9th grade in school years.

Ecology is a field of study that investigates the interrelationships of organisms in the natural world.

This substance undergoes a chemical change when heat is applied.

In this experiment, the substance will undergo a chemical change.

Gagaku is the ancient court ritual music of Japan.

He is learning the basics of elementary learning.

He clenched his lower jaw tightly to endure the pain.

There are many interests involved in this project.

The police only informed the authorized persons about the information related to the incident.

It's difficult to understand the context of this sentence.