A rhyme scheme is the pattern of rhyming lines in a poem. It is usually referred to by using letters to indicate which lines rhyme.

For example "abab" indicates a four-line stanza in which the first and third lines rhyme, as do the second and fourth. Here is an example of this rhyme scheme from To Anthea, Who May Command Him Any Thing by Robert Herrick:

Bid me to weep, and I will weep,

While I have eyes to see;

And having none, yet I will keep

A heart to weep for thee.

There are many different such forms, each with its own associations and resonances to cause a particular effect on the reader. A basic distinction is between rhyme schemes that apply to a single stanza, and those that continue their pattern throughout an entire poem (see chain rhyme). There are also more elaborate related forms, like the sestina - which requires repetition of exact words in a complex pattern.

In English, highly repetitive rhyme schemes are unusual. English has more vowel sounds than Italian, for example, meaning that such a scheme would be far more restrictive for an English writer than an Italian one - there are fewer suitable words to match a given pattern. Even such schemes as the terza rima ("aba bcb cdc ded..."), used by Dante Alighieri in The Divine Comedy, have been considered too difficult for English.

Some rhyme schemes:

• Chant royal: Five stanzas of "ababccddedE" followed by either "ddedE" or "ccddedE". (The capital letters indicate a line repeated verbatim.)
• Cinquain: "ababb".
• Clerihew: "aabb aabb".
• Couplet: "aa", but usually occurs as "aa bb cc dd ...".
• Limerick: "aabba".
• Ottava rima: "abababcc".
• Rhyme royal: "ababbcc".
• Rondelet: "AbAabbA".
• Rubaiyat: "aaba".
• Sonnet
  • Petrarchan sonnet: "abba abba cde cde" or "abba abba cdc cdc".
  • Shakespearean sonnet: "abab cdcd efef gg".
  • Spenserian sonnet: "abab bcbc cdcd ee".
  • Onegin stanzas: "aBaBccDDeFFeGG" with the lowercase letters representing feminine rhymes and the uppercase representing masculine rhymes, written in iambic tetrameter.
• Spenserian stanza: "ababbcbcc".
• Terza rima: "aba bcb cdc ...", ending on "yzy z" or "yzy zz".
• Triplet: "aaa", often repeating like the couplet.
• Villanelle: A1bA2 abA1 abA2 abA1 abA2 abA1A2, where A1 and A2 are lines repeated exactly which rhyme with the a lines.