American Heritage Dictionary of the English Language provides a definition of the term, with an etymology, including to the Indo-European root.

Brief description of this German dramatic form includes links to discussions of Mozart, Beethoven, whose "Fidelio" is technically a singspiel, and operetta.

Harvard Dictionary of Music provides a definition and short description of the German dramatic form.

Brief history of the term as used since the 16th century relates it, as a genre, to opera comique and, later, to operetta.

Singspiel referred to all German operas until the introduction of the English ballad opera, after which it was confined to dramatic works with songs and spoken dialog.

Definition of the term and description of the genre mentions that the singspiel used German rather than Italian, at the time the language of choice for most operas.