French compound nouns are made up of two or more words often
connected by hyphens. Figuring out their
gender can be a little tricky; however, the majority of compound nouns are
masculine, so when in doubt you can always fall back on that. But of course it's
better to know the gender of the words you're using, so here are some rules that
can help you to determine the gender of compound nouns.
I. Noun + noun
Gender matches that of the primary (more important) noun
un chou-fleur
cauliflower
un oiseau-mouche
hummingbird
une station-service
service station
une pause-café
coffee break
II. Adjective, adverb, preposition, or verb + noun
Gender matches that of the noun
un après-midi*
afternoon
un coffre-fort
safe
un couvre-lit
bedspread
un gratte-ciel
skyscraper
un haut-parleur
loudspeaker
un pour-cent
percent
une chauve-souris
bat
une demi-heure**
half hour
une grand-mère**
grandmother
*Après-midi can also be feminine, probably because a famous writer or two made the mistake and the Académie didn't dare correct them. :-)
**Note that the adjectives are invariable
III. Adjective + adjective
Gender matches that of the adjectives
un sourd-muet
deaf mute
une douce-amère
bittersweet, woody nightshade
IV. Exceptions to above
un brise-glace
ice breaker
un en-tête
heading
un garde-pêche
fish [and game] warden
un porte-monnaie
wallet, coin purse
un rouge-gorge
robin
un tête-à-tête
private conversation
V. The prefix mi-
Nearly always feminine
la mi-janvier
mid-January
la mi-été
mid-summer
la mi-temps
(sports) half-time
One exception: la mi-temps follows the rule and means "half-time" in sports. But there's also le mi-temps, meaning "part-time work." (More dual-gender French nouns)
VI. Other combinations (adverb + past participle or verb; verb + verb)
Usually masculine
un nouveau-né
newborn
un bien-aimé
beloved
un laissez-passer
pass
le va-et-vient
comings and goings
More: Plurals of compound nouns



