hyphens: verbs

Compound verbs may be either hyphenated or written solid. The only safe rule is to check your dictionary:

• freeze-dry
• mass-produce
• age-harden
• spoon-feed
• bad-mouth
• extra-bill

but

• waterproof
• downgrade
• sidetrack
• proofread

If the infinitive form of the verb (e.g. to air-condition) is hyphenated, retain the hyphen in all other forms, except in the case of certain gerunds (see below):

• The theatre was air-conditioned.
• You need an air-conditioning expert.

Gerunds

Hyphenate gerunds formed from hyphenated compound verbs only if they are followed by a noun object:

• Dry cleaning is the simplest way to clean a sweater.

but

• Dry-cleaning the sweater should remove the stain.
• Air conditioning is sometimes needed in summer.

but

• Is air-conditioning the building feasible?