Definitions for "En Space"
Keywords:  width, 'em, nut, blank, half
A space (between words) that will have its width equal to either the width of a capital letter "N" or "M."
Half an em. To avoid misunderstanding when instructions are given orally, typographers often speak of ems as "muttons" and ens as "nuts."
A space equal in width to an en in the font and point size selected. See EN POINT SIZE