The defining features of the Sicilian Sonnet are:
• a quatorzain, made up of an octave followed by a sestet.
• metric, in English, written in iambic pentameter.
• composed with the octave presenting an idea, problem or question, followed by a sestet finding the solution or resolution. The word “sestet” originally was reserved for the sonnet or other forms in which the group of 6 lines attempts to distinguish itself from other line groups such as the octave of the sonnet. This is in contrast to the words sixain or sexain which are 6 line stanzas usually written in conjunction with other sixains or sexains as in the Sestina.
• rhymed using only 4 rhymes. The difference between Sicilian and Italian is in the rhyme scheme. The octave made up of 2 quatrains alternates rhyme abababab. The sestet made up of 2 tercets with alternate rhyme cdcdcd.
Pasted from http://www.poetrymagnumopus.com/index.php?/topic/1048-sicilian-sonnet/
My thanks to Judi Van Gorder for years of work on this fine PMO resource.
There are three basic Italian Sonnet Forms;
2. Sicilian and
3. Sonetto Rispetto.
The difference is in the octave. The octave is constructed of two quatrains.
1. The Italian has a rhyming scheme of, a.b.b.a….a.b.b.a.
2. The Sicilian has a rhyming scheme of, a.b.b.a….c.d.d.c.
3. The Sonetto Rispetto uses uses either sestet with the Ottava Rima Octave which is very different from the two previous forms and has a rhyming scheme of a.b.a.b.a.b.c.c.
Each of these forms can also have a choice of two sestets, Italian and Sicilian:
1. The Italian sestet consists of two tercets (of 3 lines) with the rhyme scheme.. .1.2.3….1.2.3.
2. The Sicilian Sestet, has a rhyme scheme of .184.108.40.206.1.2.
Pasted from http://www.thepoetsgarret.com/Challenge/italian.html
My thanks as always to the active group at thepoetsgarret