Certain prefixes and suffixes may require a hyphen, especially to avoid awkward letter combinations or when the prefix ends, and the base word begins with the same vowel. Example: "The anti-inflammatory medication was effective." Here, the hyphen helps to avoid a jumble of vowels.

Hyphenated compound words: mother-in-law, long-term, merry-go-round Non-hyphenated compound words: bookcase, moonlight, firefly When connecting two or more compound adjectives, replace repeated words, prefixes, or suffixes with a hyphen. short- and long-term full- or part-time Three prefixes almost always require a hyphen – self-, ex-, and all-.

Certain prefixes like "self-", "ex-", "all-", and suffixes like "-elect" often require a hyphen for clarity and ease of reading.