# Glossary of Words Relating to Time

A descriptive listing of words relating to periods of time is included below. Many of the words are adjectives in form, but also are commonly used as nouns, e.g., the bicentennial of the U.S. Constitution. All terms are defined in two separate lists: first by number referred to, then alphabetically.

## Listed by Number

diurnal, per diem, quotidian
daily; of a day
nocturnal
nightly; of a night
nichthemeron
a period of 24 hours
semidiurnal
twice a day
weekly; a period of seven days
semiweekly
twice a week
biweekly
1. every two weeks
2. twice a week
fortnightly
once every two weeks
triweekly
1. every three weeks
2. three times a week
novendial
a period of nine days
monthly, tricenary
1. relating to a period of one month
2. thirty days
bimonthly
1. every two months
2. twice a month
semimonthly
twice a month
bimester
relating to a period of two months
trimester
relating to a period of three months
trimonthly
1. every three months
2. three times a month
biquarterly
twice every three months
biannual
twice a year (not necessarily at equally spaced intervals)
triannual
three times a year
semiannual, semiyearly, semestral
every half year or six-month period
annual, solennial, quotennial, per annum
yearly; once a year
biennial, biennium, biyearly, diennial
relating to a period of two years
triennial, triennium
relating to a period of three years
relating to a period of four years
quinquennial, quintennial, quinquennium
relating to a period of five years
sexennial, sextennial
relating to a period of six years
septenary, septennial, septennium
relating to a period of seven years
octennial
relating to a period of eight years
novennial
relating to a period of nine years
decennary, decennial, decennium
relating to a period of 10 years
undecennial
relating to a period of 11 years
duodecennial
relating to a period of 12 years
quindecennial
relating to a period of 15 years
septendecennial
relating to a period of 17 years
vicennial, vigintennial
relating to a period of 20 years
tricennial, trigintennial
relating to a period of 30 years
quinquagenary, semicentennial, semicentenary
relating to a period of 50 years
centenary, centennial, centennium, centurial
relating to a period of 100 years
quasquicentennial
relating to a period of 125 years
sesquicentenary, sesquicentennial
relating to a period of 150 years
bicentenary, bicentennial, bicentennium
relating to a period of 200 years
tercentenary, tricentennial, tercentennial
relating to a period of 300 years
relating to a period of 400 years
quincentenary, quincentennial
relating to a period of 500 years
sexcentenary
relating to a period of 600 years
septicentennial
relating to a period of 700 years
antemillennial, premillennial
relating to the period before the millennium
millennial, millennium
relating to a period of 1000 years; 10 centuries
postmillennial
relating to the period after the millennium
sesquimillennium
relating to a period of 1500 years; 15 centuries
bimillenary, bimillennial, bimillennium
relating to a period of 2000 years; 20 centuries
perennial
occurring year after year
plurennial
lasting for many years
aeonial
everlasting
Get all volumes of The Farlex Grammar Book in paperback or eBook.
Share Tweet

## Conversations

Site: Follow: Share:
Open / Close