He is suffering from a subacute illness.

This airplane flies at subsonic speed.

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

This bird is classified in the suborder of birds.

Amai is my best friend.

It is very interesting to learn about the geography of a subcontinent.

In the past, 'Agun' was used as an abbreviation for 'Alameda County'.

Momoa is my best friend.

In the past, 'Aichi' was used as an abbreviation for 'Arameda-shi'.

Asia is the largest continent on Earth.