Decasyllable (Italian: decasillabo, French: décasyllabe) is a poetic meter of ten syllables used in poetic traditions of syllabic verse. In languages with a stress accent (accentual verse), it is the equivalent of pentameter with iambs or trochees (particularly iambic pentameter).
Decasyllable was used in epic poetry of the Southern Slavs (for example Serbian epic poetry sung to the gusle instrument). It has also been used as the basic structure for several poetic forms in the English language including the Decasyllabic quatrain as well as in many English sonnets.
In Polish a syllabic verse line of 10 syllables can be divided by caesura into 4+6 (as in Serbian) or 5+5. The latter form was very popular at the end of 18th century. It was used in the Stanislaus stanza: 10(5+5)/8/10(5+5)/8. The name of the form refers to the reign of Stanisław August Poniatowski, the last king of independent Poland, when the stanza occurred very often. The longer lines have four accents and the shorter ones usually only three. Adam Mickiewicz wrote some of his ballads using the strophe:
Jakiż to chłopiec piękny i młody?
Jaka to obok dziewica?
Brzegami sinej Świtezi wody
Idą przy świetle księżyca.
- Adam Mickiewicz, "Świtezianka".
Medieval French heroic epics (the chansons de geste) were most often composed in 10 syllable verses (from which, the decasyllable was termed "heroic verse"), generally with a regular caesura after the fourth syllable. (The medieval French romance (roman) was however most often written in 8 syllable (or octosyllable) verse.) Use of the 10 syllable line in French poetry however was eclipsed by the 12 syllable "alexandrine" line, particularly after the 16th century. Paul Valéry's great poem "The Graveyard by the Sea" (Le Cimetière marin) is, however, written in decasyllables.
In 19th-century Italian opera, this form was often employed in the libretto. Noting its use in the operas of Giuseppe Verdi, musicologist Philip Gossett describes the composer's request to the librettist for his opera Macbeth, Francesco Maria Piave, as follows: "I'd like to do a chorus as important as the one in Nabucco, but I wouldn't want it to have the same rhythm, and that's why I ask you for ottonari" [8 syllables; and then Gossett continues] “Va, pensiero, sull'ali dorate” from Nabucco, “O Signore del tetto natio” from I Lombardi, and “Si ridesti il Leon di Castiglia” from Ernani all employ the poetic meter of decasillabi.
- Gossett, Philip, Divas and Scholar: Performing Italian Opera, Chicago: University of Chicago Press, 2008 ISBN 0-226-30482-5