Use words to express numbers under 10. Use numerals to express numbers 10 and above.

#### Also use numerals:

- in your abstract
- in measurements (5 cm)
- in mathematical functions (multiplied by 5; 3 times as many; 5% of the sample)
- when expressing time, dates, ages, scores, sums of money

#### Use words:

- when numbers appear at the beginning of a sentence
- in fractions (one fifth of the class)
- for universally accepted usages (the Twelve Apostles)

**Never use an apostrophe when expressing numbers in plural form (in the 1970s; 10s and 20s).**