He warned the young people, saying 'At thirty, one should not be careless, at forty, one should not be indecisive.'

My grandfather was born in the 1900's.

He achieved the Nine Gates in mahjong.

His actions always have a duality.

My room number is two hundred and five.

He defeated the enemy using a two-sword style.

He holds dual citizenship in America and Japan.

Carbon dioxide is one of the main causes of global warming.

This factory is emitting a large amount of sulfur dioxide.

This diode only allows current to flow in one direction.