A rhyme scheme is the pattern of rhymes at the end of each line of a poem or song. It is usually referred to by using letters to indicate which lines rhyme; lines designated with the same letter all rhyme with each other. 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. A B A B Thus 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.