"enumerable" refers to an ordering scheme that enables items in a set, sequence or collection to be readily addressed or traversed.
Enumerable is a Ruby module which can be included in other Ruby classes in order to allow iteration via #map/#collect, #select, #each, and so on.
Enumerable also manifests as the class Enumerator (documentation), which is returned when an iteration method is called without a block (e.g., array.each instead of array.each { |x| puts x }).
Enumerable objects may also utilize chained iteration, e.g., array.each.with_indices instead of array.each_with_indices.
Ruby 2.0 also introduces the concept of lazy enumeration.
In .NET, Enumerable is the class that wraps most common LINQ extension methods.
