What Is the Definition of a Cable?

Before formally explaining the definition of a cable, we can first imagine a scenario: when there is a power outage at home, the electrician comes to repair it, carrying a roll of wire wrapped in thick plastic on the outside, with visible copper cores inside — this is actually a type of cable. However, to understand it accurately, we need to first set aside its "specific appearance" and start from its "essential attributes" and "core functions" to break down and clarify the definition.
First of all, let's present the most core and universal definition of a cable: A cable is a multi-layer flexible wire consisting of a conductor, an insulating layer, an (optional) shielding layer, and a protective layer. Its core purpose is to safely and stably transmit electrical energy, electrical signals, or realize the conversion between electromagnetic energy and other forms of energy.
There are several "key words" in this definition; without any one of them, it cannot be regarded as a complete cable. Let's break them down one by one to help everyone understand more thoroughly:
The first key word is "multi-layer structure" — this is the most core difference between a cable and a "wire". The "single-strand copper core wire" we usually use to connect desk lamps and power strips has only a "conductor + a thin insulating layer" and has a simple structure; however, a cable must have a "multi-layer combination": the innermost conductor is responsible for "transmitting electricity / signals", the middle insulating layer prevents "electric leakage / signal leakage". For scenarios that require anti-interference (such as network cables and cable TV cables), an additional shielding layer will be added to block external interference, and the outermost protective layer can resist external damages such as water, fire, and corrosion. This multi-layer structure is like putting a "protective suit" on the "transmission core", allowing it to adapt to more complex environments.
The second key word is "flexible wire" — this determines the "morphological characteristics" of a cable. It is not a rigid metal tube, but a flexible, rollable "wire"-shaped structure. For example, the cable reels commonly used in engineering can roll up tens or even hundreds of meters of cables for transportation, and during construction, the cables can also be laid along the corners of walls and around pipes. If it is a non-bendable "rigid transmission body" (such as the rigid busbar on the steel tube tower used for high-voltage power transmission), it cannot be called a cable.
The third key word is "core purpose" — this clarifies the "functional positioning" of a cable. Its functions are mainly divided into three categories: first, "transmitting electrical energy", such as the cable that runs from the community substation to the home, converting high-voltage electricity into low-voltage electricity for our use; second, "transmitting signals", such as network cables transmitting network data and monitoring cables transmitting video signals; third, "energy conversion", such as the winding cable in a motor, which can convert electrical energy into mechanical energy to make the motor run. Regardless of the type of use, the core is inseparable from "safety" and "stability" — for example, power cables need to prevent electric leakage, and signal cables need to prevent interference. This is also the significance of the existence of the multi-layer structure.
Some people may ask: "So are all wires that are 'multi-layered, flexible, and transmit electricity / signals' cables?" In fact, an implicit condition needs to be added — they must be able to adapt to the needs of specific scenarios. For example, household wires can only be used in dry, low-voltage environments, while cables can cope with "complex scenarios" such as high voltage (e.g., 10 kV outdoor cables), high temperature (e.g., high-temperature resistant cables next to boilers), and underwater (e.g., submersible pump cables). In other words, a cable is an "upgraded version" of a transmission wire, designed to solve problems that "simple wires cannot handle".

In electrical engineering, communications, and related fields, a cable refers to a flexible or semi-rigid assembly designed to transmit electrical power, electrical signals, or optical signals. Its core structure typically includes one or more conductive components (such as copper or aluminum wires for electrical transmission, or optical fibers for signal transmission) and multiple protective/functional layers (e.g., insulation layers, shielding layers, and outer sheaths) that wrap around the conductors.

Cables vary widely in type based on application scenarios, transmission needs, and environmental conditions—common examples include power cables (for transmitting high-voltage/low-voltage electricity), communication cables (e.g., network cables, coaxial cables for signal transmission), control cables (used in industrial automation systems), and optical fiber cables (for high-speed optical signal transmission).