The difference of hyphen and dash

1.The hyphen (‐) is used both to join words and to separate syllables. Strictly speaking, the hyphen is not a dash at all.

For instance,there should be a hyphen in 'short-sighted'.



Examples of usage
Some strong examples of semantic changes caused by the placement of hyphens:

disease-causing poor nutrition, meaning poor nutrition that causes disease
disease causing poor nutrition, meaning a disease that causes poor nutrition
a man-eating shark is a carnivorous fish
a man eating shark is a male human in the active process of consuming shark meat

2.A dash is a punctuation mark. It is longer than a hyphen and is used differently.

Some examples of this usage:

June–July 1967
1:00–2:00 p.m.
For ages 3–5
pp. 38–55
President Jimmy Carter (1977–1981)