Nouns ending in -ment are masculine.
The suffix often marks an action or result derived from a verb.
Is sentiment masculine or feminine?
lesentiment
The rule behind it
99.6% of -ment nouns are masculine
In context
C'est parfois difficile de contrôler nos sentiments.
It's sometimes difficult to control our feelings.
Il a exprimé ses sentiments par une peinture.
He expressed his feelings in the form of a painting.
J'ai le sentiment qu'il a raison.
I have a feeling he is right.