Sinfonia (IPA: [siɱfoˈniːa]; plural sinfonie) is the Italian word for symphony, from the Latin symphonia, in turn derived from Ancient Greek συμφωνία symphōnia (agreement or concord of sound), from the prefix σύν (together) and ϕωνή (sound). In English it most commonly refers to a 17th- or 18th-century orchestral piece used as an introduction, interlude, or postlude to an opera, oratorio, cantata, or suite (Abate 1999, who gives the origin of the word as Italian) (Lotha, and the Editors of the Encyclopædia Britannica n.d.)^{[failed verification]}. The word is also found in other Romance languages such as Spanish or Portuguese.

In the Middle Ages down to as late as 1588, it was also the Italian name for the hurdy-gurdy (Marcuse 1975, p. 477). Johann Sebastian Bach used the term for his keyboard compositions also known as Three-part Inventions, and after about 1800, the term, when in reference to opera, meant "Overture" (Fisher 1998, p. 386).

In George Frideric Handel's oratorio Messiah (HWV 56), "Overture to the Messiah" (French Overture in E minor) was originally titled "Sinfony".

In the 20th and 21st centuries it is found in the names of some chamber orchestras, such as the Northern Sinfonia (Kennedy 2006).

The opening movements of cantatas BWV 31 and BWV 182^[11][12] are named "sonata" and the first movement of cantata BWV 106 "sonatina".^[13] Sinfonia in D major, BWV 1045 is considered a sinfonia of a lost cantata, because its manuscript indicates that the piece had four vocal parts.^[14]

Examples of such "sinfonias" composed after the classical era include:

• Vincent d'Indy wrote a Sinfonia brevis de bello Gallico, Latin for: "Short Symphony about the War in Gaul".^{[citation needed]}
• Igor Stravinsky titled the first movement of his 1923 Octet "Sinfonia".
• Benjamin Britten's 1940 Sinfonia da Requiem

• Sinfonia concertante
• Sinfonietta (symphony)
• Phi Mu Alpha Sinfonia
• Overture

• "Sinfonia". Encyclopædia Britannica.
• Abate, Frank R. (ed.). The Oxford American Dictionary and Language Guide. New York: Oxford University Press. ISBN 978-0-19-513449-0.
• Bach, Peter. "Werk: Vokalwerke: BWV 146: Wir müssen durch viel Trübsal". [s.l.]: Bach.de, 2004–2018 (accessed 13 May 2018).
• Bukofzer, Manfred. Music in the Baroque Era. New York, W.W. Norton & Co., 1947. ISBN 0-393-09745-5.
• Cusick, Suzanne G.; Jan Larue; John Tyrrell (2001), "Sinfonia (i)" in Stanley Sadie (ed.), The New Grove Dictionary of Music and Musicians, 2nd edition, London: Macmillan Publishers, 2001.
• Fisher, Stephen C. "Sinfonia" in Stanley Sadie (ed.), The New Grove Dictionary of Opera, Vol. Four. p. 386. London, Macmillan Publishers Ltd., 1998. ISBN 0-333-73432-7 ISBN 1-56159-228-5.
• Gardiner, John Eliot. Cantatas for the Twelfth Sunday after Trinity / Jakobskirche, Köthen. [s.l.]: Monteverdi Choir, 2007 (accessed 1 September 2017
• Kennedy, Michael. "Sinfonia". The Oxford Dictionary of Music, 2nd edition, revised, associate editor, Joyce Bourne. Oxford and New York: Oxford University Press, 2006. ISBN 978-0-19-861459-3.
• Lotha, Gloria, and the Editors of the Encyclopædia Britannica. N.d. “Sinfonia”. Encyclopædia Britannica online edition
• Marcuse, Sibyl. Musical Instruments: A Comprehensive Dictionary, corrected edition. The Norton Library. New York: W. W. Norton & Company, 1975. ISBN 0-393-00758-8.
• Randel, Don (ed.). The New Harvard Dictionary of Music. Cambridge, Massachusetts: Harvard University Press, 1986. ISBN 0-674-61525-5.