The term binary data has various meanings in different technical fields. In general, it refers to a unit of data which can take on only two possible values, traditionally termed 0 and 1 in accordance with the binary numeral system. Related concepts in various fields are *logical value (or "truth value") in logic, which represents the truth or falsehood of a logical proposition

In statistics, binary data is a statistical data type described by binary variables, which can take only two possible values. Binary data is used to represent the outcomes of Bernoulli trials, statistical experiments with only two possible outcomes. It is a type of categorical data, which more generally represents experiments with a fixed number of possible outcomes. The two values in a binary variable, despite being coded numerically as 0 and 1, are generally considered to exist on a nominal scale, meaning that they represent qualitatively different values that cannot be compared numerically. In this respect, also, binary data is similar to categorical data but distinct from count data or other types of numeric data. Often, binary data is used to represent one of two conceptually opposed values, e.g.