foil

Think of the shiny aluminum foil in your kitchen: it is a thin, flexible sheet of metal used to wrap and protect food. In stories, the word has a different sense. A foil is a character whose qualities are very different from another character's, so the other person's nature becomes easier to see. Shakespeare did this well; Laertes works as a foil to Hamlet, helping Hamlet's hesitation stand out more clearly.

The word is also a verb meaning to stop a plan from working. If a detective stops a criminal's plot, the detective foils the plan. There is also a sports meaning: in fencing, a foil is a light sword used in practice and competition. So the word can point to a thin metal sheet, a strong contrast in a story, or the act of stopping someone from succeeding.

The word "foil" works as both a noun and a verb, and it appears in a few clearly different parts of English: everyday objects, literature, and action.

First, in the most literal sense, a foil is a very thin sheet of metal. Today people often think of the aluminum foil used in kitchens, but the word can refer more broadly to thin metal layers. In earlier times, jewelers placed a metal backing behind a gemstone to reflect light and make the stone look brighter. That older image helps explain one of the word's later meanings.

In literature, a foil is a person who strongly contrasts with another person, especially the main character, so that the other character's qualities become more obvious. A calm character beside a reckless one, or a decisive person beside a doubtful one, can make those differences easier to notice. Laertes and Hamlet are a well-known example, and Dr. Watson often acts as a foil to Sherlock Holmes.

As a verb, "foil" means to stop, block, or defeat a plan or attempt. Police may foil a robbery, a guard may foil an escape, or a rival may foil someone else's scheme at the last moment. In this sense, the word usually suggests that someone was close to success but was prevented from reaching it.

The word also has a special meaning in fencing. A foil is a light, flexible sword used for training and competition. It is designed for sport, not for real fighting.

Whether you meet the word in a kitchen, a novel, a news story, or a fencing match, the idea stays fairly consistent: one thing either brings another into clearer view or stops it from going forward.