Nouns ending in -ence are usually feminine.
The suffix forms abstract nouns, often from verbs.
Is adolescence masculine or feminine?
l'adolescence
The rule behind it
97.6% of -ence nouns are feminine
In context
L'adolescence est souvent une période d'insécurité.
Adolescence is often a period of insecurity.
Sami était à la fin de l'adolescence.
Sami was in his late adolescence.
Je ne me suis pas senti comme ça depuis mon adolescence.
I haven't felt like this since I was a teenager.