An aria is an extended operatic solo.
Any operatic solo is called an aria.
Sometimes arias are called scenas, aria or scena in the singular.
a solo by a singer is called an "aria". It is essentially one voice singing by itself without any other voices.
An aria.
scena
Jessye Norman sang a solo called Tannhauser by Wagner. Jessye did this at her operatic debut at the Deutsche Opera Berlin.
Not sure if this is what you're looking for, but an operatic solo is referred to as an aria.
aria
Aria
An extended opera solo
An operatic song is called an aria. This is a solo song that is a self contained piece that can be with or without instrumental music.