Ai is my best friend.

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.

Will you marry me?

"Do you want to have a meal? Take a bath? Or choose me?" she said jokingly.