Using hyphens to join prefixes to root words

A hyphen can be used to join a prefix to a root word but there are no set rules. Hyphens are more commonly used to prevent two vowels appearing next to each other e.g. re-enter and co-ordinate. Hyphens are often used with the prefixes ex- and self- e.g. ex-president and self-care. Hyphens can join a prefix to a root word to avoid ambiguity in meaning e.g. re-cover or recover. How to spell the curriculum words: interrupt and exaggerate.