Question

What do you mean by well define collection with an example

Answer 1

What does it mean for a set to be well-defined?
            A set is well-defined if there is no ambiguity as to whether or not an object belongs to it, i.e., a set is defined so that we can always tell what is and what is not a member of the set.

Example:  C = {red, blue, yellow, green, purple} is well-defined since it is clear what is in the set.