A rhyme scheme is a regular pattern of rhyme, one that is consistent throughout the extent of the poem. Poems that rhyme without any regular pattern can be called rhyming poems, but only those poems with an unvarying pattern to their rhymes can be said to have a rhyme scheme.
The following short poem illustrates the labeling of a rhyme scheme.
There once was a big brown cat a
That liked to eat a lot of mice. b
He got all round and fat a
Because they tasted so nice. b
This bit of elegant verse shows a very simple rhyme scheme. The first rhyme sound we encounter, at the end of the first line, is cat. Because it is the first rhyme sound, it is labeled as a. Every time that rhyme sound is repeated, any time something rhymes with cat, it is also called a. Line three ends with fat, which rhymes with cat, so it is also an a.
The second rhyme sound comes at the end of the second line, mice. As the second rhyme sound it is called b, and so are any other following lines that rhyme with it, such as nice in line four.
