How to say and write numbers in English?

Fractions and decimals

We say simple fractions like this:

1/8 = one eighth

5/7 = five sevenths
2/5 = two fifths
3/4 hour = three quarters of an hour

More complex fractions are usually expressed by using the word over.
218/576 = two hundred and eighteen over five hundred and seventy six

We say and write decimals like this:

0.278 = nought point two seven eight (US zero point two seven eight)
(NOT nought point two hundred and seventy eight)

Nought, zero, nil etc

The figure 0 is usually called nought in British English, and zero in American English. When we say numbers one figure at a time, 0 is often called oh.

My phone number is nine three two five oh six (= 932506)

In measurements of temperature , 0 is called zero in both British and American English.

Zero scores in team games are called nil. In tennis and similar games, the word love is used for zero.

And the score is: Brazil three, Italy nil.
Forty-love: Nadal to serve

Telephone numbers

Each figure is said separately. There is usually a pause after groups of three or four figures. If the same figure comes twice, British people usually say double.

657 4481 – six five seven, double four eight one (British)
– six five seven, four four eight one (US)

Roman numbers
The names of kings and queens are still written in Roman numbers.

It was built in the time of Louis XIV.
Queen Elizabeth II
Henry V

Cardinal and ordinal number

The numbers one, two, three, four etc., are called cardinal numbers whereas the numbers first, second, third, fourth etc., are called ordinal numbers. Ordinal numbers are used before nouns. After a noun, we use cardinal numbers.

the fourth chapter – chapter four
the third act – Act Three