Hyphens

You could see evidence of a hyphen debate taking place right on the screen. Clearly one person who had control of the ticker favored hyphens and another person who also had control of the ticker did not.

The hosts noticed and started talking about it themselves. Fun stuff!

How to Use Hyphens

It turns out the first person was on the right track. In the sentence Is the glass half full? you don't need a hyphen between half and full. However, if we put the words half full before the word glass so that they are acting as a compound modifier, then it makes sense to use a hyphen. The sentence would read He was holding a half-full glass.

Now, the detail-oriented people among you will notice that I didn't say anyone was right or wrong, and I didn't use strong words such as should hyphenate or must hyphenate. I chose my words carefully because the rules about hyphens can hardly be called rules; there are so many exceptions it's making me crazy.

The safest thing to do when you're unsure about hyphenating is to look the words up in a dictionary. For example, the Oxford English Dictionary generally recommends hyphenating half-full when it comes before a noun and not hyphenating it otherwise, but the dictionary also shows exceptions. It's also common for published and in-house style guides to have a list of compound words that should be hyphenated. For example, The Chicago Manual of Style has a long guide to hyphenation and states that most compounds that begin with the word half are hyphenated when they come before nouns. So, my advice is to check a dictionary or style guide, but if you don't have one handy, follow the rule that you hyphenate compound modifiers when they come before a noun, and don't hyphenate them when they come after a noun.

Here's another example:

• They were in a long-term relationship. (In that sentence, I hyphenated long-term because it comes before the noun relationship. Long-term is a compound adjective that modifies the word relationship.)
• Their relationship was long term. (No hyphen. I didn't hyphenate long term because it comes after the noun.)

Hyphens Can Change a Sentence's Meaning

Sometimes it is especially important to hyphenate the compound modifier because words can mean different things depending on the hyphenation. When you hyphenate the words, you are applying them as a single unit to the noun.

For example, there's a difference between a hot-water bottle with a hyphen and a hot water bottle without a hyphen. When you hyphenate hot-water, you're making it a single compound modifier that applies to the word bottle. It's a bottle for holding hot water. But when you don't hyphenate hot water, the words are separate modifiers and you're describing a water bottle that is currently hot.

• A hot-water bottle is a bottle for holding hot water.
• A hot water bottle is a water bottle that is hot.

Always consider whether hyphenation will affect your meaning.

In-Word Hyphenation

Meaning also matters when you are trying to decide whether to use a hyphen within a word. For example, if you didn't press your jeans properly and you need to re-press them, you would write that with a hyphen: I need to re-press my jeans. Otherwise, people might think you mean the verb repress meaning "to stifle or put down." You re-press jeans, but repress bad memories.

• You need to re-press your jeans.
• You need to repress those bad memories.

A dictionary is also helpful for figuring out less obvious cases of in-word hyphenation. Fortunately, there are at least a few solid rules. You use a hyphen when when you're joining a prefix to a word that must be capitalized and when joining a letter to a word. For example, you use a hyphen in

• Anti-American
• Un-American
• Pre-Mesozoic
• X-ray
• A-list
• T-shirt

Also, you use hyphens to write out numbers from twenty-one to ninety-nine. For example

• Thirty-five
• Sixty-four
• Ninety-three