Cavatina

It is now frequently applied to any simple, melodious air, as distinguished from brilliant arias or recitatives, many of which are part of a larger movement or scena in oratorio or opera.

[1] "Ecco, ridente in cielo" from Gioachino Rossini's opera The Barber of Seville, "Porgi amor" and "Se vuol ballare" from Mozart's The Marriage of Figaro are well-known cavatinas.

A famous piece that bears the name, although without words, is the 5th movement of Beethoven's String Quartet in B-flat major, Opus 130.

It developed in the mid-18th century, coincident with the decline of the previously favoured da capo aria (in which the musical form is ABA, with the repeated A section given improvised variations).

In 19th-century bel canto operas of Bellini, Donizetti, and Verdi the term came to refer to a principal singer’s opening aria, whether in one movement or paired with a contrasting cabaletta.