frein

/fʁɛ̃/
1.
nounmasculine

brake (mechanical device used to slow or stop a vehicle or machine)

Le frein de mon vélo ne fonctionne plus.

The brake on my bike isn't working anymore.

2.
nounmasculine

hindrance; obstacle; restraint (something that slows down or prevents progress)

Le manque d'argent est un frein à mon projet.

The lack of money is a hindrance to my project.