1. The hyphen (-) joins two equally emphasized words:
The morning’s blue-black cold
Noah Munley-Hanscom
The restaurant was famous for
its man-eating shark.

2. The dash (—) separates two ideas

3. ABRUPT CHANGE: Use dashes to indicate an abrupt change in thought in a sentence or an emphatic pause:
We will fly to Austin in May – if the
convention isn’t cancelled.
Fox offered a plan – it was
unprecedented – to raise revenues.

4. SERIES WITHIN A PHRASE:
When a non-essential-phrase that otherwise would be set off by commas contains a series of words that must be separated by commas, use dashes to set off the full phrase:
He listed the budget items – advertising,
sales, and fundraisers – that would be in
next year’s budget.

5. ATTRIBUTION:
Use a dash before an author’s or composer’s name at the end of a quotation:
“Who steals my purse steals trash.” –Shakespeare

6. There are two kinds of dashes:
The Em dash is longer and goes between two words with no spaces.
Em dash  — Option + Shift + hyphen
The En dash is shorter and goes
between two words with a space on
either side.
4. EN dash – Option + hyphen

7. EM DASH:
He listed the budget items—advertising,
sales and fundraisers—that would be in
next year’s budget.
EN DASH:
He listed the budget items – advertising,
sales and fundraisers – that would be in

8. NEVER use a hyphen when a dash is called for!
DON’T EVER DO IT, HOLMES:
NEVER use a hyphen when a dash is called for!
NEVER use two consecutive hyphens to indicate a dash!