The use of prose and verse is often used to show a separation of class
Aristocratic, upper class character tend to speak in verse
used when addressing other upper class and when self analyzing
Servants, lower class speak more in prose
This is a base idea; a place to start. Shakespeare breaks from this pattern numerous times throughout his cannon.
An interesting example in The Tempest is Caliban's use of verse. While this could easily be explained by the fact that Propsero and Miranda (noble borns) teach him language, Shakespeare give Caliban some of the most beautiful verse that appears in his works.
In can also tell us the mental state of a character.
For example, in Macbeth, Lady speaks mostly in verse during the first half of the play, but in Act 5 Scene 1 (the sleep walk scene; "Out, damned spot! Out I say!") she speaks entirely in prose. This indicates to the actor that there is a change happening within the character.
"Written text without a formal metrical structure OR you can think of it like how people normally spoke"
We have already talked about how it can be used to distinguish lower characters from higher, but Shakespeare wrote in prose for a variety of reasons. He used it for comedic effect like in much ado about nothing, to speak towards a character's mental stability like what we have investigated with Lady Macbeth, and to make more realistic dialogue.
For example, much of Hamlet's text is written in prose. Shakespeare breaks Hamlet's verse with prose, giving him some of the most humanistic realizations in the play.
"I have of late—but wherefore I know not—lost all my mirth, forgone all custom of exercise; and indeed it goes so heavily with my disposition that this goodly frame, the earth, seems to me a sterile promontory. This most excellent canopy the air, look you, this brave o’erhanging, this majestical roof fretted with golden fire—why, it appears no other thing to me than a foul and pestilent congregation of vapours."
- Hamlet, Hamlet Act 2 Scene 2
At the time Shakespeare was writing, verse was seen to show literary excellence. So by writing in prose, Shakespeare was breaking from the societal convention, much like many of his characters.
"Written text with a set rhythm or meter."
The majority of Shakespeare's plays are in verse (some are eveb written entirely in verse). Shakespeare wrote mainly in blank verse meaning there is a rhythm to the text, but no rhyme. The verse is used to convey heighten emotion and ideas. The poetical language and rhythm allows the actor to be carried and supported by the play. The language is a vessel that gives actors the agency to explore the big ideas and complex feelings Shakespeare explores.
Example:
"But soft, what light through yonder window breaks?
It is the East, and Juliet is the sun.
Arise, fair sun, and kill the envious moon,
Who is already sick and pale with grief
That thou, her maid, art far more fair than she.
Be not her maid since she is envious;
Her vestal livery is but sick and green,
And none but fools do wear it. Cast it off."
- Romeo, Romeo and Juliet Act 2 Scene 2
Fun Fact: Tempest is written in approximately 80% verse!