Numbers are classified in grammar into two main groups: Cardinal and Ordinal.

Numbers serve as adjectives‏‎ in that they modify the noun which follows, e.g.

There are young people here.

There are many people here.

There are six people here.

Note that in a sentence such as:

There are thirty here.

the number is still an adjective but the noun is assumed:

There are thirty [people/biscuits/houses] here.

Note that some grammars class numbers as determiners‏‎ or quantifiers‏‎.

Cardinal Numbers

We use cardinal numbers to answer the question, how many?

1, 2, 3, 4… 40, 50, 60, 100

one, two, three, four… forty, fifty, sixty… one hundred

Ordinal Numbers

We use ordinal numbers to answer the question, in which order?

first, second, third, fourth… fortieth, fiftieth, sixtieth, hundredth

the first person to arrive

Tim was the second child.

Kathryn Parr was the sixth wife of Henry the Eighth.

To create an ordinal number, just add -th to the cardinal spelling:

four > fourth

nine > ninth

The exceptions are:

one > first

two > second

three > third

five > fifth

eight > eighth

nine > ninth

twelve > twelfth

In writing, we can use a shorthand of

1st, 2nd, 3rd, 4th… 40th, 50th, 60th, 100th

In other words,we use just the last two letters of the ordinal number. Note also that in compound ordinal numbers only the last figure is written as an ordinal number:

62nd = sixty second

143rd = hundred and forty third

0 – Zero

As a cardinal number, 0 has several different forms:

• oh (as in telephone numbers, 007, etc)
• nought (as in mathematics, etc)
• nil (as in football scores, etc)
• nothing (as in scores, etc)
• zero (as in mathematics, telephone numbers, science, etc)
• love (as in tennis: thirty-love)

It is also a special case in that it does not have an ordinal version.

Fractions/Decimals

When we deal with a smaller number than 1, we use either fractions or decimals:

three and a quarter – two and a half – twenty-six and three-quarters

3¼ – 2½ – 26¾

three point two five – two point five – twenty six point seven five

3.25 – 2.5 – 26.75

Roman Numerals

Roman numerals are used in select cases, notably in titles and sometimes as year dates. In titles we add a the between the title and the number:

Henry VIII > Henry the Eighth

John IX > John the Ninth

Exceptions are cases like Word War II which is said as World War Two.

In Writing

In writing we can use either digits:

1,234.5

or we can spell out the number:

one thousand two hundred and four point five

Good style guides suggest you should use a word at the beginning of a sentence but, if the writing is informal, you can use a digit inside the sentence.

Three cars tried to overtake the four buses.

Three cars tried to overtake the 4 buses.

* 3 cars tried to overtake the four buses.

* The asterisk is used to show this is an error.