The context affects some of the above definitions and terminology. The equivalence of this GCD definition with the other definitions is described below. There are several different sociological definitions and descriptions for the term. Scholars continue to try to reach definitions and define boundaries. The following definitions and attributes are relevant. Examples for these definitions are found easily. This is expressed in terms of class definitions. Competing practical definitions of probability reflect philosophical differences. The following definitions all involve the term formula 50. The term altcoin has various similar definitions. Measurements demand the use of "operational definitions" of relevant quantities. They are particularly useful for explaining complex hierarchies and overlapping definitions. A summary of the more significant definitions follows. Below are some of the commonly used definitions. They differ slightly from some of the definitions given below.