Cycle
A cycle is a collection of cards that have one or more relationships with one another and consists of one card for each color or color combination.
A simple cycle, usually just called a cycle, consists of five cards, one in each color, in the same set.
More complex cycles include mega cycles, mega-mega cycles and Ravnica block cycles.
Examples of simple cycles
The simplest cycle has five cards, one for each individual color, each with a similar card type, function, and sometimes mana cost and name.