Hyphen usage examples for compound modifiers

Last Updated : Dec 09, 2022 |

Use a hyphen between the following types of compound modifiers:

Type of compound modifier

Examples

Number + noun

10-digit number

Adjective + noun

High-level description

Noun + noun

Parent-child hierarchy

Number + abbreviation

2-GB cartridge tape drive

Numbers spelled out from 21 to 99

Twenty-eight candles

Time

Three-thirty train

Adjective + participle

Open-ended question

Noun + adjective

User-centric design

Exception for common compound modifiers

Some modifiers are used as a single concept and do not require a hyphen for clarity. The following table provides examples of compound modifiers that do not need hyphens:

Term

Examples

Call progress

Call progress tones

Central office

Central office switch

Class of service

Class of service options

Cut to service

Cut to service procedures

Direct inward dialing

Direct inward dialing trunks

Hard disk

Hard disk drive

Long distance

Long distance access code

Message waiting

Message waiting indicator

Switch hook

Switch hook flash

Voice messaging

Voice messaging system

Voice response

Voice response application