Eighty is also:

The atomic number of mercury

A cross-country interstate in the United States

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, Sinclair ZX80, and 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, and F-80 Shooting Star

part of the name of the bands Eighty-D and Eighty Proof Soul

the upper age limit for cardinals to vote in papal elections

the percentage of consequences that stem from 20% of the causes according to the "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 80A, 80B and 80C photographic filters correct for excessive redness under tungsten lighting

The ISBN Group Identifier for books published in the Czech Republic and Slovakia.

The year AD 80, 80 BC, or 1980.

The title of the 8th track on Green Day's second full length album Kerplunk!