Nouns ending in -ance are feminine.
The suffix forms abstract nouns, often from verbs.
Is connaissance masculine or feminine?
laconnaissance
The rule behind it
100% of -ance nouns are feminine
In context
J'ai fait sa connaissance l'année dernière.
I got acquainted with him last year.
Il a la connaissance ainsi que l'expérience.
He has knowledge and experience as well.
C'est plus une connaissance qu'une amie.
She is more of an acquaintance than a friend.