I thought thousand was a compound word of thous-and, but I see that thou is just slang for thousand. That would render the and as unnecessary but not strictly wrong.
1,234,567,890 is
one billion twohundred thirty four million five hundred sixty seven thousand eight hundred nintey.
Ands get used in such a number for emphasis or breathing space.
Note from darts the high score 180 is allways pronounced one hundred and eighty. For emphasis 666 is often pronounced six hundred and sixty six.
In any list you put the first few words separated by commas, then AND, and then the last word
e.g. David, Sally AND John went to the cinema
Therefore you say when reading a number like 1,234:
One thousand, two hundred and thirty-four (thirty-four being hyphenated counts as one word, so you don’t say thirty and four). Simple rules of grammar kids…
If there’s a decimal point we say 1,234.5 as One thousand, two hundred and thirty-four point five (in Ireland and Britain as far as I know anyway).
Still, languages develop so whatever comes into common usage where ever you live is ‘right’ I suppose. They’re just different dialects of English - RP (Received Pronounciation I think) English, American-English, Hiberno-English (that’s the Irish version BTW) etc.
that’s my two cents worth.
I’ve lived in Australia, Canada, the UK, and the United States.
In my experience, Aussies and Brits nearly always say “and,” Canadians sometimes do, and Americans almost never do.
It’s not a matter of right or wrong, just of different usage.
I think Mr. Adams himself explained this one. My 2 cents: call this year Naughty Three. 
Think about it - sixties, seventies, eighties, nineties, naughties!
At long last our decade has a name.
Should I say he explained why “aught” is misheard from “naught”. Sorry, I don’t have enough time to search for the article.
I was taught in the US never to use “and” when talking numbers. Grew up in the 50’s-60’s. We were always admonished if we put an “and” into any number.
I do like living in the naughties though.
The news director on the station I wake up to says this. It’s annoying.
Do those people refer to Stanley Kubrick’s or Arthur C. Clarke’s space odyssey as “Twenty-Oh-One”?
“Two thousand three” is a number.
“Two thousand and three” is the statement of an arithmetic problem, the answer to which is “Two thousand three.”
No, but they should. Do you refer to the year 1901 as one thousand nine hundred one? I didn’t think so.
1901 = nineteen oh one. Why should 2001 be any different?
Not quite.
2000 = 0x11111010000; 3 = 0x11;
0x11111010000 ^ 0x00000000011 = 0x00000000000
Therefore two thousand and three equals zero.
However, two thousand or three equals two-thousand-three.
Which is why these kind of threads (the other ones of the kind being those about regional accent and national spelling conventions, sometimes religion too) are often so amusing - it is really very easy to imagine that the usage to which you personally are accustomed, is objectively the best and only true and logical way.
Two-thousand-three is a number
Two-thousand AND three is a math problem
As I see Early Out agreed with too
This is true in some localities, including America, but elsewhere (such as in the UK…
Two throusand AND three is a number
Two thousand three is a list comprising two numbers; 2000, 3
Well, no. A list with only two members would be spoken as “two thousand and three.” A list with three members would be “two thousand, one hundred, and three.”
And where’s Opal when we need her?!
It’s a beat. It’s a rhythm thing. Part of the natural rhythms of speech. Holds the place mentally for speaker and listener; warns listener on almost unconscious level to expect last number. That helps listener organize memory to keep the whole number in short-term memory. Small numbers don’t need a beat because they don’t approach the seven-number limit of things you can keep in short-term memory.
None of this is science. All my two cents’ worth. But I feel the need for the “beat” very strongly in a long number. If you approach talking as a form of music instead of a subset of math transfer, it all makes more sense.
Two thousand plus three and two thousand add three, are two maths problems. The answer to each problem is two thousand and three 