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

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

gauche

play

lacking social experience or grace

Words at Play

alt-59721dd897313

The 'Best' Way to Sign Off On An E-mail

Give them your best

Words and Phrases That Come from the Dinner Table

Fill your plate with these surprising food words

ghost-being-disinvited-from-party

'Disinvite' or 'Uninvite'?

A disinvited guest is an uninvited problem

alt-596f730ceb5ae

Words We're Watching: 'Scoby'

Kombucha lovers unite.

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

The Emoji Quiz

Think you’re an emoji 👓 expert? Let’s see 🤔

Take the quiz

A Game of Thrones Word Quiz

In the Game of Thrones quiz, you learn some new vocabulary. (It’s quite safe, really. You will not die.)

Take the quiz

How Strong Is Your Vocabulary?

How Strong Is Your Vocabulary?

Test your vocabulary with our 10-question quiz!

Take the quiz

SCRABBLE® Sprint

SCRABBLE® Sprint

SCRABBLE® fans, sharpen your skills!

Play the game