Grammar lesson on how hyphens and dashes work

Hyphens link words together.

When words have to work together as a unit to describe something, hyphens tie them together.

example: three-month-old boy

He is not a three boy.

He is not a month boy.

He is not an old boy.

He is a three-month-old boy. The words have to join together into one unit to describe the boy.

Examples from https://owl.purdue.edu/owl/english_as_a_second_language/esl_students/punctuation/hyphens_and_dashes.html

• • • • There are fewer Italian-American communities these days.
      • The family’s money-saving measures have been helping them to build their savings.
      • She has stopped buying 2-liter bottles and has started buying 0.5-liter bottles, instead.

WHAT DASHES ARE FOR

(note: a dash is typed by typing two hyphens in a row)

Dashes highlight parts of a sentence.

We have already seen that when you are adding extra information to a sentence (usually a sentence that is grammatically correct without the addition) you can separate that information with...

parentheses ( ) to downplay the information:

The year he was born (1968) his mother and father bought a farm.

or

commas , , when the added information is about as important as the rest of the sentence.

The street behind McCreless, Dewey Street, is faculty parking only.

Dashes -- -- emphasize and highlight the addition. 

The parking ticket-- which he got for parking on Dewey Street-- cost $200!