En space is a term used in typography to describe a specific amount of space that is the width of a letter "n". However, there are several synonyms for en space that are often used interchangeably, depending on the context in which they are used. Some of these synonyms include "em space", "quad space", and "half space". An em space is twice the width of an en space and is the width of the letter "m". A quad space is four times the width of an en space, while a half space is half the width of an en space. Each of these terms has a slightly different meaning but can often be used in place of each other depending on the needs of the document being prepared.