EIGHTY encyclopedia topics

In mathematics

The sum of Euler's totient function φ(x) over the first sixteen integers is 80.

Adding up some subsets of its divisors (e.g., 1, 4, 5, 10, 20 and 40) gives 80, hence 80 is a semiperfect number.

Messier object M80, a magnitude 8.5 globular cluster in the constellation Scorpius
The New General Catalogue object NGC 80, a magnitude 12.1 spiral galaxy in the constellation Andromeda
The Saros number of the solar eclipse series which began on 333 BC June 13 and ended on 929 July 9. The duration of Saros series 80 was 1262.1 years, and it contained 71 solar eclipses. Further, the Saros number of the lunar eclipse series which began on 121 BC January 27 and ended on 1213 April 6. The duration of Saros series 80 was 1334.2 years, and it contained 75 lunar eclipses.

Eighty is also:

A rectifier vacuum tube manufactured from the mid-1920s through the mid-1980s, the longest production run of any American vacuum tube.
The number Ronaldinho now wears for the Italian football club, AC Milan.
The atomic number of mercury
A cross-country interstate in the United States
Iowa 80 truck stop, the world's largest truck stop
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
in the title of the film "Star 80" (1983) starring Mariel Hemingway
in the title of the film 80 Steps to Jonah (1969) starring Wayne Newton
the model number of the computers TRS-80, Sinclair ZX80, and Aster CT-80
the model number of:

part of the name of the bands Eighty-D, Eighty Proof Soul and Element Eighty
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 York; the European route E80 from Lisbon to Gürbulak
the standard TCP/IP port number for [] connections
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 Audi 80, the predecessor to the Audi A4.
The title of the 8th track on Green Day's second full length album Kerplunk!
The highest score possible on each of the three sections of the PSAT
Eighty shilling ale
According to Exodus 7:7, Moses was 80 years old when he initially spoke to Pharaoh on behalf of his people.