SINCE 1828

An Encyclopædia Britannica Company

aleph-null

play

noun \ -ˈnəl \

Definition of aleph-null

:the number of elements in the set of all integers which is the smallest transfinite cardinal number

First Known Use of aleph-null

circa 1909

Learn More about aleph-null

See words that rhyme with aleph-null Britannica.com: Encyclopedia article about aleph-null

Seen and Heard

What made you want to look up aleph-null? Please tell us where you read or heard it (including the quote, if possible).

show

WORD OF THE DAY

shofar

play

a ram's-horn trumpet used in Judaism

Words at Play

alt-59c4207ecf106

Let's Talk 'Tea'

Spill it, sip it: just make it hot.

8 Words and Phrases from Boxing and Wrestling

Common terms that come from boxing and wrestling

alt-59c2960017c94

The Ambiguity of Pushing 'Up' and 'Back'

When you push a meeting, where does it go?

Silent Letters

When each letter can be seen but not heard

Ask the Editors

video-title-words-of-the-year-1066

Words of the Year: 1066

Or, Why Pig Meat is Called 'Pork' and Cow Meat is Called 'Beef'

How Often Is 'Biweekly'?

Don't get us started on 'bimonthly'

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless

Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals

Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

young-plant-shoots

Merriam-Webster's New Words Quiz—Fall 2017 Edition!

You're going to have to memorize the dictionary again.

Take the quiz

stylized-drawing-of-woman-pole-vaulting-across-gap-to-get-trophy

Challenging Vocabulary Quiz Returns!

No tricks, just difficult words.

Take the quiz

Spell It

Can you spell these 10 commonly misspelled words?

Take the quiz

Bee Cubed

Listen to the words and spell through all three levels.

Play the game