What is defined as one binary number consisting of either 1 or 0?

A binary number consisting of either 1 or 0 is defined as a bit. The term "bit" is derived from "binary digit," and it represents the most basic unit of data in computing. All digital data is ultimately composed of bits, which are used to convey information in binary form.

In the context of the other options, a byte is typically made up of 8 bits and serves as a larger unit of data storage, while a nibble consists of 4 bits. A word can vary in size depending on the computer architecture but generally refers to a standard unit of data that a processor handles at one time, often equal to 16, 32, or 64 bits. Thus, while bits are foundational and crucial to computing, the other choices represent larger units that are constructed from multiple bits.