What is a clone (algebra)?
In algebra, a clone is a set of operations on a given set that is closed under composition and includes all projection maps.

More specifically, let S be a non-empty set and let Ar(S) denote the set of all finite sequences of elements of S. A clone on S is a set of operations on S that satisfies the following properties:

1. If f and g are operations in the clone, then the composition fg is also in the clone.
2. For every element a in S, the projection map P(a) is in the clone, where P(a)(x) = a for all x in S.

The clone generated by a subset T of S is the smallest clone containing all operations in T. The notion of a clone is important in the study of algebraic structures, particularly in universal algebra, where it is used to define and study the properties of algebraic structures such as groups, rings, and fields.