Letters A and B are members of the
What about J?
What is special about A,E,I,O and U?
Is there a collection whose members are colours (red, orange, yellow, green, blue, teal, antique white, ...)?
The `spectrum' perhaps? Or is there more to it?
The collection whose members are map grid-reference points in the UK?
The collection of points in the UK to which these grid-references correspond?
Sort yourself (if you can) into a group according to the following sequence of
Female/Male; Young/Old; Religious/not; Football fan/not; Music fan/not; ...