There are a lot of fun, informal words in English to describe really big numbers!

As you know, large numbers in English all end in -illion [pronounced /ɪljən/].

1,000,000 (million)
1,000,000,000 (billion)
1,000,000,000,000 (trillion)
1,000,000,000,000,000 (quadrillion)

As you also know, we like to make up words in English! There are many made-up words in English that you can use to talk about big numbers. These are NOT real numbers! These are words that children often use when they don’t know the word for a big number. Adults use these words when they want to exaggerate a number or when they want to be funny. These words can also be used when you don’t know the exact number of something, but you know the number is huge!

zillion /’zɪljən/

gazillion /gə’zɪljən/

bazillion /bə’zɪljən/

jillion /’ʤɪljən/

bajillion /bə’ʤɪljən/

katrillion /kə’trɪljən/

… really, you could add any prefix to -illion and make it a word!
Example Sentences:

Wow, have you seen Mr. Smith’s new Porsche? It must have cost him a bajillion dollars!

If I were a zillionaire*, I would buy a huge house in Beverly Hills, California.

There are a gazillion stars in the sky!

The beach was so crowded today. There must have been a jillion people there!

I am telling you for the gajillionth** time, don’t wear your shoes in the house!

 

Notes:
*People who are very wealthy can be described by adding -illionaire [pronounced /ɪljənɛɚ/] to the number:

He’s a millionaire! (= he has a million dollars or more)
She’s a billionaire! (= she has a billion dollars or more)
I don’t think anyone is a trillionaire … yet!

**Adding -th to a number makes it an ordinal number (i.e., first/1st, second/2nd, third/3rd, fourth/4th, fifth/5th, etc.). It shows the position of something, the position in a series, or how many times something has been done.

These are all informal words. You wouldn’t use these words in a formal business setting, for example if your boss asks you for a sales estimate, or if you are talking to a co-worker about how many items your company has sold.

 

Real-world examples:

SendGrid Raises $5 Million, Sends A Bajillion E-mails (TechCrunch.com)

London’s New Multi-Bajillion Dollar Thames Estuary Airport Hits a Snag (Jaunted.com)

Who wouldn’t want to be Tim Cook? The guy runs the most valuable company in the world, makes a gazillion dollars a year, and everybody wants to be his best buddy. (cnet.com – an article about the new Apple CEO)

Jeep campaign in a katrillion little pieces? (Adweek.com)