I have done my best to accurately describe the different poetic forms I have used here, but in my research, have occasionally run across differing definitions. In those instances, I use what seems to be the more popular definition. For a more detailed description, I would urge you to google it.
(Note: When a rhyme scheme is given, capital letters mean the line is written verbatim.)
In Alphabetical Order:
American Cinquain–an unrhymed, 5-line poem that has a set number of syllables per line. The 1st line has 2 syllables; the 2nd, 4; the 3rd, 6; the 4th, 8; and the 5th, 2 (2-4-6-8-2). It is typically written in iambs.
Blank Verse–does not rhyme but is written with a precise meter–almost always using iambic pentameter, which has 10 syllables per line. It has no fixed number of lines.
Constanza–created by Connie Marcum Wong, consists of five or more 3-line stanzas. Each line has a set meter of eight syllables. The first lines of all the stanzas can be read successively as an independent poem, with the rest of the poem weaved in to express a deeper meaning. The first lines convey a theme written in monorhyme, while the second and third lines of each stanza rhyme together. Rhyme scheme: a-b-b, a-c-c, a-d-d, a-e-e, a-f-f. (Definition is taken from Poets Collective. Introduction – Poetry Forms (poetscollective.org)
Crown Cinquain—a series of 5 (entire) Crapsey Cinquains, 25 lines total. Syllable count per line 2, 4, 6, 8, 2 in each stanza, written with breaks between stanzas. Rhyme is optional. The last line of the previous cinquain is repeated as the first line of the next cinquain. The final line of the last cinquain does not have to equal the first line of the first cinquain but is optional. (Credit for the definition goes to Abigail Gronway at Dark Side of the Moon.)
Etheree–consists of 10 lines of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 syllables. The lines can be reversed in order—10, 9, 8, 7, 6, 5, 4, 3, 2, and 1. A Double Etheree has 20 lines of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 9, 8, 7, 6, 5, 4, 3, 2, and 1. It can also be written in reverse order.
Free Verse–does not contain rhymes, strict meter, or the use of repetition. It has varied meter but can use loose iambic pentameter and cadence.
Haiku—a form of Japanese poetry, a traditional haiku contains just 3 lines with a total of 17 syllables. The 1st line has 5 syllables; the 2nd, 7; and the 3rd, 5. But in its modern form, the length of a line can vary as long as it follows a short/long/short format. A haiku is usually about nature (or elements of nature) and has two parts: a sentence fragment on the 1st or last line, and the other two lines are the body of the haiku. It is written in the present tense, taking place in a moment in time, and doesn’t use metaphors, similes, personification, or other common poetic devices. It is an essence of a moment.
Kyrielle Sonnet–consists of 14 lines (three rhyming quatrain stanzas and a non-rhyming couplet). Like the traditional Kyrielle poem, the Kyrielle Sonnet also has a repeating line or phrase as a refrain (usually appearing as the last line of each stanza). Each line within the Kyrielle Sonnet consists of only eight syllables. French poetry forms have a tendency to link back to the beginning of the poem, so common practice is to use the first and last line of the first quatrain as the ending couplet. This would also reinforce the refrain within the poem. Therefore, a good rhyming scheme for a Kyrielle Sonnet would be: A-a-b-B, c-c-b-B, d-d-b-B, A-B or A-b-a-B, c-b-c-B, d-b-d-B, A-B. (Definition is taken from Shadow Poetry.)
Quatrain–consists of 4 lines of rhyming verse, but the rhyme scheme is not set. There are 15 possible rhyme schemes with a-b-a-b being the most common. The poem can consist of a single verse or multiple verses.
Rhyme Royal—verse is 7 lines long, 10 syllables per line. Rhyme scheme: a-b-a-b-b-c-c)
Rondeau–has 15 lines containing 3 stanzas—a quintet, a quatrain, and a sestet. Lines 9 and 15 are short: a refrain consisting of a phrase taken from the 1st line. Rhyme scheme: a-a-b-b-a, a-a-b-R, a-a-b-b-a-R.
Rondel–based on two rhyme sounds and consisting of two quatrains followed by a quintet—13 lines total—or a sestet—14 lines total. The first two lines of the 1st stanza are repeated as the refrain of the 2nd and 3rd stanzas. The meter is open but usually has eight syllables per line. Rhyme scheme: A-B-b-a, a-b-A-B, a-b-b-a-A or B.
Senryu—A form of Japanese poetry similar in construction to haiku but is usually concerned with human nature, satiric humor, and political issues. A senryu’s tone is what sets it apart from a haiku.
Sestina–a strict ordered form of poetry, dating back to twelfth-century French troubadours. It consists of six 6-line (sestets) stanzas followed by a 3-line envoy. Rather than use a rhyme scheme, the six ending words of the first stanza are repeated as the ending words of the other five stanzas in a set pattern. The envoy uses two of the ending words per line, again in a set pattern. First stanza,..1 ..2 ..3 ..4 ..5 ..6. Second stanza, ..6 ..1 ..5 .. 2 ..4 ..3. Third stanza, ..3 ..6 ..4 ..1 ..2 ..5. Fourth stanza, ..5 ..3 ..2 ..6 ..1 ..4. Fifth stanza, ..4 ..5 ..1 ..3 ..6 ..2. Sixth stanza, ..2 ..4 ..6 ..5 ..3 ..1. Concluding tercet: middle of first line ..2, end of first line ..5. Middle of second line ..4, end of second line..3. Middle of third line ..6, end of third line ..1) Rhyme scheme: a-b-a, a-b-a, a-b-a, a-b-a, a-b-a, a-b-a-a.) (Definition taken from Shadow Poetry.)
Shakespearean Sonnet (English)—has 14 lines divided into 3 quatrains and a couplet. Each line typically has 10 syllables written in iambic pentameter. Rhyme scheme: a-b-a-b, c-d-c-d, e-f-e-f, g-g.
Terzanelle–a combination of the villanelle and terza rima poetic forms, it consists of 19 lines containing 5 interlocking tercets, plus a concluding quatrain, in which the 1st and 3rd lines of the 1st tercet appear as refrains. The middle line of each tercet is repeated, reappearing as the last line of the succeeding tercet, with the exception of the center line of the next-to-last stanza, which appears in the quatrain. Each line has the same metrical length. Rhyme and refrain scheme: A-B-A, b-C-B, c-D-C, d-e-D, e-F-E, f-A-F-A, or f-F-A-A. (Definition taken from Shadow Poetry.)
Villanelle–has a fixed form, written in tercets, usually five in number, followed by a final quatrain, all based on two rhymes. The 1st and 3rd lines of the 1st stanza are repeated as the last line of the following stanzas in alternating order throughout the poem and appear together as the last two lines in the final quatrain.
ZaniLa Rhyme—created by Laura Lamarca, consists of 4 lines per stanza. The rhyme scheme for this form is a-b-c-b and has a syllable count of 9-7-9-9 per stanza. Line 3 contains internal rhyme and is repeated in each odd-numbered stanza. Even stanzas contain the same line but are swapped. The ZaniLa Rhyme has a minimum of 3 stanzas and no maximum poem length. (Definition taken from Shadow Poetry.)