A hanging or suspended hyphen can be used when you have 2 or more words that have the same base word but different prefixes or first words. The first instance of the base word is deleted, and the hyphen shows the link to the base word:

first- and second-year students     inter- and intracellular

When to use hanging hyphens

Hanging hyphens are useful for:

  • comparing or contrasting 2 things
macro- and microeconomic policy  
  • reducing the repetition of long words
pro- and anti-establishment groups  
  • making numeric lists more readable
5-, 10- and 15-year droughts     19th- and 20th-century artists     fourth- and fifth-level teachers

But you do not have to use a hanging hyphen in any of these situations. It will often be clearer if you simply spell both words out in full. This is particularly important if your audience has lower reading abilities:

low-rise and high-rise buildings   instead of   low- and high-rise buildings 

How to use hanging hyphens

For compounds with a hyphen, use a hyphen with both prefixes:

short- and long-term solutions     full- and part-time consultants

For compounds that would normally be set solid, use a hanging hyphen with the prefix of the first term:

pre- and postnatal     under- and overestimate

Do not use hanging hyphens for base words with different suffixes or last words, because they are usually difficult for the reader to understand:

lifeguard and lifeboat training   not   lifeguard and -boat training

he was caught red-faced and red-handed   not   he was caught red-faced and -handed