Eighty (80, LXXX) is the natural number following seventy-nine and preceeding eighty-one.
- Hexadecimal: 50
- Binary: 01010000
- Greek numeral: π´
- Factors: 1, 2, 4, 5, 8, 10, 16, 20, 40, 80
- Factorization:
- Ordinal number: eightieth
- Numeral system base 80: octagesimal
- Name in other languages: quatre-vingt (in French, from four and twenty), see also wiktionary:eighty
80 is also:
- the atomic number of mercury (Hg)
- the number of units in a fourscore
- the age at which one becomes an octogenarian
- in the title of Around the World in Eighty Days by Jules Verne
- the model number of the computers TRS-80, IBM 80, Sinclair ZX80, Aster CT-80
- the model number of T-80, a Soviet tank; IAR 80, a Romanian WWII fighter aircraft; McDonnell Douglas MD-80, Arado Ar 80, F-80 Shooting Star
- part of the name of the bands Eighty-D and Eighty Proof Soul
- the age limit for cardinals to vote at papal conclaves
- the percentage of work done with 20% of the resources according to a "80/20 rule"
- the length of a beach in Western Australia: Eighty Mile Beach
- the length of the Eighty Years' War or Dutch revolt (1568-1648)
- the number of the French department Somme
- the designation of Interstate 80, a freeway that runs from California to New Jersey; the European route E80 from Lisbon to Gürbulak
- the standard TCP/IP port number for HTTP connection
- the year AD 80 or AD 1980.
