Half-month is a term that typically refers to a period of fifteen days. There are many synonyms for this term that can be used in different contexts. One common synonym is "fortnight," which is derived from an Old English term meaning "fourteen nights." Another synonym is "biweekly," which can refer to something that happens every two weeks or to a period of two weeks. Still another synonym is "semi-monthly," which is often used to describe pay periods that occur twice a month. Some other possible synonyms for half-month include "half a month," "fifteen days," and "two weeks".