I would say that the opera component for a solo performance is called ARIA.
This is an elaborated song for a solo voice, just one voice. It can be written for the main character focusing on his/her emotions. The term means "air" in Italian and it is connected to a melody by performed by a singer. It might be accompanied by an orchestra.
The United States was willing to pay more per mile for the Gadsden Purchase than for the Mexican Cession because the Gadsden Purchase gave money to the United States to build a railroad.
