This is the 16639th most frequent Russian word.
сердец
"Сердец" is the genitive plural form of "сердце," meaning "hearts."
Here, 'сердца' is used to denote the plural form of 'сердце' (heart) as entities being filled with emotional essence.
Любовь наполняет сердца радостью.
Love fills hearts with joy.
In this sentence, 'сердцами' refers to the instrument or characteristic related to these individuals, expressing their emotional state.
У дверей стояло трое молодых людей с разбитыми сердцами.
Three young people with broken hearts stood near the door.
Here, 'сердец' is in the genitive plural form, indicating possession or extent related to emotional impact.