One of the first major differences you'll encounter moving from English to French is that nouns have gender - either masculine or feminine.
This is a feature of all Romance languages (e.g. Italian, Spanish, Portuguese).
There are two challenges:
So how do you determine if a word is masculine or feminine?
This is the short word that comes before the noun.
If the article is un, le, du, or ce, then the word is masculine.
If it's une, la, de la, or cette then the word is feminine.
Most of the time, you can use this rule which covers a lot cases (but not all!).
Nouns that end in -age (fromage/cheese), -ment (moment/moment), -eau (ruisseau/spring), -phone (téléphone/telephone), -scope (téléscope/telescope), or -isme (capitalisme/capitalism) are masculine.
Nouns that end in -tion (condition/condition), -sion (persuasion/persuasion), -té (volonté/will), -ette (tablette/tablet), -ance (endurance/endurance), -ence (violence/violence), -ie (scie/saw), -ure (sciure/wood shavings), -ode (cathode/cathode), -ade (promenade/walk), -ude (solitude/solitude) are feminine.
You can usually take a stab at the feminine form of a word by adding an e to the end of the masculine form.
Examples:
un patient - une patiente (a patient)
déterminé - déterminée (determined)
Of course, it's not always that easy.
There are a lot of exceptions.
Occasionally, you'll find that the feminine form of a noun doesn't even resemble the masculine form! (cheval/stallion, jument/filly)
Just like English, most French nouns can be written as plurals by adding an (s) to the end of the word:
chat/chats (cat/cats)
voiture/voitures (car/cars)
However, there are several classes of exceptions you should know about.
prix (award or price)
poids (weight)
nez (nose)
The spelling of these words doesn't change between the singular or plural.
Examples:
vitrail - vitraux (stained glass window(s))
général - généraux (general(s))
tuyau - tuyaux (pipe(s))
Notable exceptions that end with s in the plural:
bal - bals (ball(s))
carnaval - carnavals (carnival(s))
festival - festivals (festival(s))
récital - récitals (recital(s))
portail - portails (portal(s))
Examples:
neveu - neveux (nephew(s))
eau - eaux (water(s))
4) The following nouns that end in ou in the singular end in x in the plural
bijou - bijoux (jewel(s))
caillou - cailloux (stone(s))
chou - choux (cabbage(s))
genou - genoux (knee(s))
hibou - hiboux (owl(s))
joujou - joujoux (little toy(s))
pou - poux (louse(s))