Which of the following is used to represent a binary digit?

A binary digit is represented by the term "bit," which is the fundamental unit of information in computing and digital communications. A bit can have a value of either 0 or 1, which aligns perfectly with the binary system's base-2 numeral system. This representation is crucial because all digital data, including text, images, and sounds, is ultimately encoded in binary form, making bits the building blocks of computer systems.

The other options refer to larger units of data or concepts in computing. A byte, for example, comprises eight bits and is often used as a basic addressable element in many computer architectures. A word typically represents a set of bits that are processed together by a computer, which can vary in size according to the architecture (commonly 16, 32, or 64 bits). A character usually refers to a symbol represented in computing, such as letters, numbers, or punctuation, often encoded using a specific standard like ASCII, where each character can occupy one or more bytes depending on its encoding.

Understanding that a bit stands as the smallest unit of data reinforces the concept that it is the core building block for all other larger data representations in computer science.