In poetry, a stanza is a group of lines that are read together, usually united around a common theme or idea. It is a unit of poetry composed of lines that relate to a similar thought or topic, like a paragraph in prose or a verse in a song. Stanzas are used to provide structure, rhythm, and organization to a poem. They guide the reader from one idea to the next and group similar ideas and thoughts together. The structure of a stanza is determined by the number of lines, the dominant meter, and the rhyme scheme. There are various types of stanzas that are typically defined by the number of lines, such as tercet or terza rima (three lines) and ottava rima (eight lines). Some stanzas are named for their inventors or best-known practitioners or for the work in which they first were heavily used. For example, the Spenserian stanza is named for Edmund Spenser, and the In Memoriam stanza is popularized by Alfred, Lord Tennyson in the poem by that title.