numbers: spelled-out numbers

In technical writing, use numerals rather than spelled-out numbers.

• The sample weighs 2 g.
• The height of the object is 7 cm.

In non-technical writing, as a general rule, write out one-digit numbers, and use numerals for the rest.

• Jane saw five Canada geese at the lake.
• We walked 15 km.

Ordinals should be treated in the same way as cardinal numbers

• seven and seventh
• 101 and 101st

The rules stated above are guidelines for general use, but note that there are a number of exceptions. For detailed guidelines on individual cases, see our series of articles on numbers.