A funnel is a device for directing the flow of a solid or liquid substance into a desired container or location. Simple funnels consist of a hollow cone with openings on each end. Material is poured into the wide end and directed out through the narrow end. Versions of this device are used in numerous fields, from cooking to chemistry to auto maintenance. Anything that has a similar shape or function may also be called a funnel.
Funnels are typically made of materials that are sturdy, chemically inert, and easy to clean. Most are designed for repeated use over long periods of time, although disposable funnels are also widely available and easy to create. Any flexible, durable material, such as sheets of cardboard or thick-stock paper, can be curled into makeshift funnels if necessary. Small funnels serve a wide variety of uses, such as transferring foods and beverages into containers, or adding motor oil to a car engine. Large funnels made of tough materials are used in the production and transport of industrial substances, such as liquefied cement, metal or glass.
The processing of chemicals, whether in laboratory or industrial settings, requires specialized kinds of funnels. Some have valves called taps, which allow the flow of material to be precisely controlled or cut off entirely. This is useful for work that requires exact amounts of a certain substance. Special funnels called separatory funnels are used to control the rate and amount of combination of two or more chemicals. Others are equipped with filters, to separate denser materials out of liquids or powder; this is one of the most common uses of funnels.
The term “funnel” is also commonly used to describe the smokestack on a ship or a train. This kind of funnel directs rising steam or smoke from the engines into the air, away from the vehicle and its passengers. The word also describes various natural phenomenon, such as tornadoes, which are commonly called “funnel clouds” if they do not touch the ground. The funnel-web spider employs this distinctive shape to catch prey, as does the carnivorous plant called the pitcher plant. The device is common enough that the word is frequently used to describe any object that would more accurately be termed “conical.”
The word is also used to describe metaphorical constructs. Anyone who diverts money from various sources into a single enterprise, legal or otherwise, is often said to be “funneling” funds. It is also possible to funnel information, or even people, in this way. Internet users, for example, tend to filter themselves out with each step required to make a purchase from a web site: the more steps involved, the fewer people will actually make a purchase. Web designers and programmers refer to this phenomenon as a “conversion funnel.”