One of the largest differences between prose and sonnets is their language. Prose is defined by its use of ordinary, everyday language and flow. The straightforward language often changes to suit the particular purpose. For instance, academic prose used in a thesis has significantly different language and flow than a short story, with the thesis containing more technical terms and formal language. A sonnet's language is typically very descriptive and florid, though contemporary poets may use terse, simple language, but the language is bound by rhyming rules. Sonnet language also tends to focus more on a word's musical nature.
Next to language, prose and sonnets have very different arrangements. Simply looking at a sonnet and piece of prose tells you that sonnets have a set number of lines, and you can typically see a rhyme and meter pattern right away. Prose is largely written in complete sentences, with each sentence beginning with a capital letter. The sentences form paragraphs. Sonnets must adhere to a particular rhyme scheme and pattern as well, usually based in iambic pentameter, so each line, or foot, has five stressed syllables.
Sonnets typically muse on two contrasting ideas, images, emotions or sides of a story or issue. Each side of the subject matter is placed next to the other for pondering. The poet thus tells the reader or audience something about those two things to highlight a tension or sometimes harmony in their relationship. Prose typically shows different ideas through a narrative or straightforward address, sometimes in comparison or contrast, and sometimes completely different ways — through characters in a novel and the themes they embody, for instance.
Writers sometimes mix prose and the sonnet. An English prose sonnet uses 14 sentences to tell a narrative. The last word in each sentence rhymes with the last word in another sentence. The traditional rhyme scheme follows that of an English sonnet — ababcdcdefefgg. Each sentence also has an internal rhyme with the last word of that sentence. Similar to traditional English sonnets, the last two sentences form a couplet, their last words rhyming with one another, and the content summarizes or casts new light on the story, sometimes adding irony.