From Polyglot Club WIKI
There’s a pair of punctuation marks in English that are frequently misused or unused. This is due to the fact that the proper use of these marks must be understood properly. The punctuation marks in question are the hyphen and the dash.
The hyphen (-) is a punctuation mark that is used for various purposes which include: connecting words, writing compound numbers, dividing words into syllables, etc. On the other hand, the dash (according to Merriam Webster’s Dictionary) is a punctuation mark used to show a break in thought or in structure of a sentence.
How to write the hyphen (-)
The hyphen is written as a very short horizontal line (-) at the middle of the height of the lowercase letters in a text. Example: multi-purpose. The hyphen is much shorter than the dash.
How to write the dash (–)
The dash is written as a short horizontal line (–) at the middle of the height of the lowercase letters in a text. The dash is much longer than the hyphen. It is nearly three times the size of the hyphen. From the above, it is clear that the dash and the hyphen can be easily told apart.
Use of the hyphen (-)
The hyphen is used in some cases to add a prefix to a word: co-debaters, ex-wife, etc. Note: Words which have their prefixes attached using a hyphen must always be written with the hyphen.