A fortnight (sometimes fourtnight) is a unit of time equal to 14 days (2 weeks). The word derives from the Old English: f?owertyne niht, meaning "fourteen nights".
Some wages and salaries are paid on a fortnightly basis; however, in North America it is far more common to use the term biweekly. Neither of these terms should be confused with semimonthly, which divides a year into exactly 24 periods (12 months × 2), instead of the 26 (?52 weeks ÷ 2) of fortnightly/biweekly.
In astronomy, a lunar fortnight is half a lunar synodic month, equivalent to the mean period between a full moon and a new moon (and vice versa). This is equal to 14.77 days.
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A fortnight is a term that is used prominently in sporting circles - as many major sports events have a two-week or approximately half-month time frame. In tennis, Wimbledon and the other Grand Slam tournaments are played over two weeks and are often referred to as lasting a fortnight. The Summer and Winter Olympics are also slightly longer than two weeks in length and may be referenced in this manner as well. Likewise various other events in the sporting world could fall under this characterization.
In other languages
In many languages, there is no single word for a two-week period, and the equivalent terms "two weeks", "14 days", or "15 days" (counting inclusively) have to be used.
- Celtic languages: in Welsh, the term pythefnos, meaning "15 nights", is used. This is in keeping with the Welsh term for a week, which is wythnos ("eight nights"). In Irish, the term is coicís.
- Similarly in Greek the term ? (dekapenthímero), meaning "15 days", is used.
- The Hindu calendar uses the Sanskrit word "paksha", meaning one half of a lunar month, which is between 14 and 15 solar days.
- In Romance languages there are the terms quincena (or quince días) in Galician and Spanish, quinzena or quinze dies in Catalan and Portuguese, quindicina in Italian, quinze jours or quinzaine in French, and chenzin? in Romanian, all meaning "a grouping of 15"; there are also the terms bisettimanale in Italian, bisemanal in Spanish, bissemanal in Portuguese, bisetmanal in Catalan, bihebdomadaire in French, and bis?pt?mânal in Romanian, that literally mean "biweekly".
- Semitic languages have a special "doubling suffix". When added at the end of the word for "week" it changes the meaning to "two weeks". In Hebrew, the single-word ? (shvu?ayim) means exactly "two weeks". Also in Arabic, by adding the common dual suffix to the word for "week", , the form ? (usbu?ayn), meaning "two weeks", is formed.
- Slavic languages: in Czech the terms ?trnáctidenní and dvoutýdenní have the same meaning as "fortnight".