The fourth book – Book Four
The third act – Act Three
He is in class nine. OR He is in the ninth class.
However, the names of kings and queens are said with ordinal numbers.
Louis XIV: Louis the Fourteenth
Elizabeth II: Elizabeth the Second
Ordinal numbers up to twelfth are written in words, except in dates. Cardinal numbers up to twelve are written in words, except when telling the time.
Cardinal and ordinal numbers above twelve and twelfth are written in either words or figures as seems in each case the more convenient.
British people always use and before the tens in a number. In American English, and can be dropped.
Four hundred and fifty 450 (GB/US)
Four hundred fifty 450 (US)
Two thousand, three hundred and forty two (2,342)
In writing we generally use commas to divide large numbers into groups of three figures, by separating off the thousands and the millions. Note that we do not use commas in dates.
4, 564, 453
The year 1979