Decimal Notation

The hyphen you can insert with the key next to the zero on your keyboard is an ambiguous character suffering from an identity crisis.
It can't decide if it's a hyphen -, a minus −, an em dash — or an en dash –.

The Unicode specification describes the key as a hyphen-minus and defines very specific replacements for its use.

Use it to insert a hyphen, but never for a minus or a dash, since it does not have the correct width for either, or the vertical position for the latter.

Neither an em dash nor an en dash should be confused with the hyphen, which has the following functions:

1. To join compound words together.
2. To connect compound words
3. To connect the syllables of words broken at the ends of lines
4. To connect prefixes and suffixes to words

The modern trend is away from hyphenation, and to eliminate the hyphen after a prefix.

Hyphens are always required with the following prefixes:

• half
• quarter
• quasi
• self
• ex
• all

1. The non-breaking hyphen ‑ does just what its name implies.
2. The soft hyphen ­ also known as a discretionary hyphen is used for one purpose only —to indicate where a word may be broken at the end of a line.
   Otherwise, it is to remain invisible and not affect the appearance of the word.
3. The hyphen character ‐ is meant to be used in place of the hyphen-minus when a hyphen is exactly the desired character.
4. The hyphen point ‧ is that bullet-like character you find in some dictionaries to separate syllables. That is its only use, but if you’re creating an online dictionary, using it will make your entries look more professional.
5. The hyphen bullet ⁃ is a version of the hyphen character ‐

Permanent compounds tend to become solid, and temporary compounds tend to be hyphenated only when necessary to avoid ambiguity.

hyphens are not dashes

The quote below illustrates the use of the hyphen -, the en dash – and the em dash —. In some fancy fonts the difference is more than just the width — hyphens have a distinct serif.

"Re-read the book — at least 2–3 times — then let it sink in."

"Re-read the book — at least 2–3 times — then let it sink in."