Akiko is my best friend.

Arisa is my best friend.

He is suffering from a subacute illness.

This species has different characteristics depending on its subgroup.

This airplane flies at subsonic speed.

I learned about the reaction of nitrous acid in chemistry class.

Hypochlorous acid is a hypo compound of chlorine.

The children were happily playing Kagome Kagome in the park.

Primates are a part of mammals, which also includes humans.

Primates, known as '霊長目' in Japanese, is a classification that includes many mammals, including humans.