Hyphens are the short lines that separate the words in expressions like ex-husband and make-up.

Two-part adjectives in which the second part ends in –ed or –ing are often separated by hyphens.

Green-eyed monster
Blue-eyed boy
Good-looking guy
Broken-hearted fellow

Two-part adjectives which express the sense of ‘between’ are also hyphenated.

A Mumbai-Beijing flight
India-Pakistan match
The Anglo-French agreement

Longer phrases that are used as adjectives before nouns are also hyphenated.

An out-of-work dancer

In British English, two-word compound nouns are usually hyphenated when the stress falls on the first word.

A paper-shop
Running-shoes

The prefixes co-, non-, and ex- are sometimes separated from what follows by hyphens.

Co-production
Ex-wife
Ex-husband
Ex-lover
Ex-minister
Non-cooperation
Non-alignment

Are hyphens disappearing?

Hyphens are now becoming less common. That is probably because the rules are complicated and usage is not very common.

Many short compounds are now written with no division between the words. Examples are: weekend, takeover etc. Less common or more complex words are now written as completely separate words. Examples are: truck driver, bus conductor, living room etc. The situation is rather confused at the moment. Needless to say, we often find the same expression spelt in three different ways. Examples are: bookstore, book-store and book store.