Using M-dash and N-dash?

[Geoff Hart <ghart -at- videotron -dot- ca>]

Abhijit Sinha wondered: <<Can you please explain the differences in the 
use of M-dash and N-dash>>

Any good style guide will explain the usage of these symbols and 
provide many examples; the Chicago Manual of Style provides a good 
overview.

Quickly: An en dash is so-named because it's the width of the letter n 
(sometimes N) in the same font, whereas an em dash is the width of the 
m (sometimes M). Use an en for ranges (10-20), low temperatures (-20C), 
and in place of a hyphen in an open compound (e.g., Microsoft 
Word[en]induced frustration). Use an em for parenthetical 
interruptions--such as this one--in the middle of a sentence.

<<Also please let me know if there is any difference between legal 
english and normal english (American or British).>>

Legal English (the language of lawyers) bears the same relation to 
normal English that French bore to English in the century after the 
Norman conquest: it's the result of a small group of people conquering 
a much larger group and taking away control of their language. Over 
time, one can hope that the larger mass of the people will revolt and 
regain control of their own language, but given that it's the lawyers 
who make the laws, this could prove difficult. <g>

Less facetiously, legal English is a dialect with its own jargon, 
usage, and style conventions, and you can't understand that dialect 
until you understand these unique aspects of it. I've been a 
professional editor for something like 20 years, and still don't claim 
to understand legal English--but you can certainly find legal editors 
who do understand, and they're the ones you should ask about this.

--Geoff Hart   ghart -at- videotron -dot- ca
(try geoffhart -at- mac -dot- com if you don't get a reply)