hyphens: fractions

Follow the guidelines below in deciding whether to use a hyphen in a fraction written in words.

Fractions used as adjectives

As a rule, hyphenate fractions used as adjectives and written in full:

• a one-third share
• a three-fifths majority

Fractions used as nouns

Usage is divided on whether fractions used as nouns should be hyphenated. Some style guides prefer to omit the hyphen in such fractions:

• Four fifths of the load was wheat, and one fifth barley.

However, the traditional practice (and the one still recommended in most style guides) is to hyphenate fractions whether they are used as adjectives or as nouns:

• Four-fifths of the load was wheat, and one-fifth barley.

Exception

When either the numerator or the denominator is a number that already contains a hyphen, do not add a second hyphen:

• twenty-nine hundredths (not twenty-nine-hundredths)
• one thirty-second (not one-thirty-second)