doz‧en S2 W3 /ˈdʌzən/ number (plural dozen or dozens) (written abbreviation doz.)
[Date: 1200-1300; Language: Old French; Origin: dozeine, from doze 'twelve']

1. twelve:
a dozen eggs
two/three/four etc dozen (=24, 36, 48 etc)
The number of deaths has risen to more than two dozen.
dozens of people/companies/cars etc (=but not hundreds or thousands)
Dozens of people were killed.
Chris, Helen, and half a dozen others went on holiday together.
A dozen or so (=about 12) cars were parked near the entrance.

2. informal a lot of
a dozen
I’ve heard this story a dozen times before.
dozens of something
She’s had dozens of boyfriends.
We collected dozens and dozens of shells on the beach.
⇒ BAKER’S DOZEN, ⇒ a dime a dozen at dime(2), ⇒ nineteen to the dozen at nineteen(2), ⇒ six of one and half a dozen of another at six(4)

[TahlilGaran] Dictionary of Contemporary English ▲

dozen
number
Using numbers
Day, month, minute, mile, kilo etc are always SINGULAR when used (with a number) immediately before a noun: ‘a six-minute wait’, ‘a ten-second silence’, ‘a five-mile race’.
My travel agent had arranged a 6-day coach tour.
The company provides a three-month training course.
Compare: ‘We waited for thirty minutes: ‘We had a thirty-minute wait.’
When you say 100, 1000 etc , or write these numbers in words, use a hundred, a thousand (WITH a ):
The palace was build a thousand years ago.
Compare: ‘The palace was built 1000 years ago.’
For emphasis or to be exact, it is possible to use one instead of a :
I am one hundred percent against the idea.
After a/one/five/twelve etc , the words hundred, thousand, etc are always SINGULAR and are NOT followed by of :
Five hundred children are born in the city every day.
More than three thousand people were there.
Similarly, of is NOT used after 100, 250, 3000 etc:
If you kill 200 whales a year, they will soon disappear.
Hundreds (of), thousands (of) etc are used only when you give a general idea of how many or how much: ‘There were hundreds of stars in the sky.’ ‘They’ve spent thousands (of pounds) on improvements to the house.’
Use and between hundred and the next number. (In American English, and is often omitted, especially in formal styles.)
BrE The club has about a hundred and thirty members.
AmE The club has about a hundred (and) thirty members.

[TahlilGaran] Dictionary of Common Errors ▲

dozen
ˈdʌzn
See: by the dozen , daily dozen , dime a dozen , six of one and half-a-dozen of the other

[TahlilGaran] English Idioms Dictionary ▲