em, ex, en? Which length units are font size dependent?

Question

Length can be specified as 3em, or 3.5ex. What is required to make 4en also valid? Are there any other font related length units?

em is not the width of a character m!!! so your comment about the width of an i seems misplaced, you can use \fontcharwd to find the width of a character in a font. — David Carlisle, Aug 15 '16 at 09:55

score 12 · Accepted Answer · edited Apr 13 '17 at 12:35

12

There is no en unit. TFM fonts have font dimensions 5 and 6 which may be accessed as ex and em no other fontdimen corresponds directly to a unit.

see

What do different \fontdimen<num> mean

Note in comments you ask about the width of an i you can use e-tex \fontcharwd to find the width of a character or classically \setbox0\hbox{i}... \wd0 But this em and ex are not related to the width or height of the m and x characters they are just arbitrary lengths assigned by the font designer.

edited Apr 13 '17 at 12:35

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answered Aug 15 '16 at 10:02

David Carlisle

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But there is an \enspace macro, which has sometimes lured me into thinking en is defined as a unit in LaTeX. – alephzero Aug 15 '16 at 12:58
there's a \bigskipamount as well but that isn't a unit either, – David Carlisle Aug 15 '16 at 12:59
True enough, but en is (or was, historically) a common printing term - often called a "nut" to distinguish it clearly from a "mutton" (em) when speaking. – alephzero Aug 15 '16 at 13:05
@alephzero I know:-) but... – David Carlisle Aug 15 '16 at 13:07

em, ex, en? Which length units are font size dependent?

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