He received the letter challenging him to a duel and began preparing for the duel.

Gender roles are an important element in defining individual behavior in society.

His role is to fulfill his responsibilities as a leader.

Please use the emergency stairs in case of a fire.

Due to the earthquake, the city declared a state of emergency.

He underwent an examination of the hard palate.

This mineral is called anhydrite.

Beautiful scale clouds were spread across the sky.

Tridymite, a type of high-temperature quartz, is often found in volcanic rocks.

The leaves of the scale tree are arranged in scales, as the name suggests.