On the meaning of string.length

[Adam D. Ruppe via Digitalmars-d-announce]

On Wednesday, 19 November 2014 at 21:00:50 UTC, Ary Borenszweig 
wrote:
> In Ruby `length` returns the number of unicode characters

What is a unicode character? Even in utf-32, one printed 
character might be made up of two unicode code points. Or 
sometimes, two printed characters might come from a single code 
point.