Secondary characters are reoccurring characters who are of lesser importance than the primary or main characters. Secondary characters who function as a contrast to the major characters are called foils. In Shakespeare's classic play Romeo and Juliet, Mercutio serves as Romeo's foil. Mercutio is considered Romeo's foil because he expresses a different opinion on love and has opposite character traits. Unlike Romeo, who is passionate and serious about love, Mercutio mocks love and is rather cavalier about the subject. Mercutio is also portrayed as charismatic and enthusiastic while Romeo is depicted as depressed and melancholy before attending the Capulet ball. Another secondary character who acts as a foil is Rosaline. Rosaline is Juliet's foil and is portrayed as aloof and uninterested in Romeo. Unlike Juliet, who is infatuated and loyal to Romeo, Rosaline has sworn off marriage and remains distant. Overall, foils are secondary characters who contrast primary characters, and both Mercutio and Rosaline act as foils in the play.

A secondary character who serves to contrast the traits of a major character, often the protagonist, is called a foil.  Rosaline, for example, serves as a foil to Juliet.  Rosaline is, apparently (for she never appears on stage), emotionally distant and does not return Romeo's affections; in fact, she has sworn to remain chaste and never indulge in fleshly pleasures.  Juliet, on the other hand, is very passionate and romantic, and she marries Romeo within twenty four hours of meeting him for the first time.

Tybalt, Juliet's cousin, also serves as a foil for Benvolio, Romeo's cousin.  Benvolio, as the root of his name suggests, is good and peace-loving.  He is constantly trying to break up fights between the Capulets and Montagues, and he encourages others to use good sense in their dealings.  Tybalt, on the other hand, hates peace and seems to thrive on violence.  He often instigates fights himself or adds fuel to the disagreements begun by others.  Their contrast makes Tybalt seem so much more evil and Benvolio so much more benevolent.