òssia

Ossia is a musical term used in notation to indicate an optional alternate passage. The term comes from Italian o sia, meaning "or that is," signaling that the passage is an alternative to the main line.

Notationally, ossia passages are typically printed in smaller notes or in a separate staff and marked with the word ossia. They may offer an easier version of a difficult passage, a more elaborate version for advanced players, or a different musical idea entirely.

Ossia passages are intended to be optional; performers may choose to play the main version or the ossia, depending on the edition, performance context, or skill level. Editors sometimes include ossias to aid learners, while composers occasionally used them to present alternatives within a single work.

While most commonly encountered in piano repertoire, ossia appears across instrumentals and vocal music. Notable usage evolved in the classical period and has persisted into modern editions and arrangements.

Orthography: The standard spelling is ossia. Some texts may render the headword as òssia, reflecting pronunciation or editorial choice, but this is less common.