What is the term for a binary number that can only be 1 or 0?

A binary number that can only be 1 or 0 is referred to as a bit. A bit is the most basic unit of data in computing and digital communications, representing a state of information that can either be on (1) or off (0). This duality of the bit allows computers to represent and manipulate data using binary code, which is the foundation of all digital computing.

In contrast, a byte consists of 8 bits and serves as a larger grouping of binary data. A nibble consists of 4 bits, essentially half of a byte. The term "word" typically refers to a fixed-sized group of bits that a computer's processor can handle as a single unit, and its size can vary depending on the architecture of the computer. Therefore, the correct term that fits the description of a binary number that can only be 1 or 0 is indeed a bit.