What type of noun is separated by a hyphen?

One type of compound noun is a hyphenated compound noun. Examples:

• A-frame
• forty-five
• mother-in-law
• not-for-profit
• six-pack
• T-shirt
• U-turn
• warm-up
• x-ray
• year-end

The other types of compound nouns are:

open compounds; paint brush, seat belt, shoe store

closed compounds; bathtub, bedroom, scoreboard