Nouns are not always singular in both French and English. Here is a list of words that are singular or uncountable, or have unmarked plurals in English but are plural or countable in French.
advice conseils
ammunition munitions
asparagus asperges
audience spectateurs, auditeurs
baggage, luggage bagages
broccoli brocolis
business affaires
to cause damage causer des dégâts
chess échecs
clothing vêtements
contact information / name and address coordonnées
damage dommage(s),* dégats
data** données
debris débris
deer cerf(s), biche(s)***
deposit arrhes
to do research faire des recherches
engagement fiançailles
evidence preuve(s)***
to feel remorse éprouver des remords
fish poisson(s)***
forecast prévisions
fruit fruit(s)***
funeral funerailles, obsèques
furniture meubles
garbage, rubbish déchets, ordures
gift (for Christmas or New Year's) étrennes
graffiti graffitis
hair cheveux
hay foins*
herringbone chevrons
holiday (British English) vacances
homework devoirs
income revenu(s), rente(s)*
information informations, reseignements
knowledge connaissances*
lovemaking ébats amoureux/sexuels
math (American English) maths
medicine médicaments
offal abats
pasta pâtes
progress progrès*
quicksand sables mouvants
rubble décombres
science sciences*
sheep mouton(s)***
software logiciel(s)***
spaghetti spaghettis
spinach épinards
static parasites
there's a good chance that
il y a de fortes chances que
transportation transports
vacation vacances
vicinity environs
volcanic smoke and gas fumerolles*
*These are usually but not always plural in French
**Data is actually the plural of datum, but it is commonly used as a singular noun in English
***These nouns are uncountable in English but countable in French
In addition, many adjectives that are used as nouns when referring to a group of people are singular in English, but have plural French equivalents:
the dead les morts
the living les vivants
the poor les pauvres
the rich les riches
the sick les malades
the young les jeunes
etc
If you can think of any other singular/uncountable English nouns that are plural in French, please let me know and I'll add them here.
English singulars, French plurals | French singulars, English plurals

