This is the 16641st most frequent Russian word.
сердечный
"Сердечный" means "heartfelt," "warm," or "cordial."
Here, 'сердечное' is used as an adjective to describe 'дружелюбие' (friendliness), emphasizing its warmth and sincerity originating from the heart.
Её сердечное дружелюбие сразу располагает к себе.
Her heartfelt friendliness immediately draws people to her.
The word 'сердечным' conveys being 'dear' or 'close,' demonstrating an intimate and emotional bond with the family.
Он стал сердечным другом нашей семьи.
He became a dear friend of our family.
In this context, 'сердечные' refers to physical issues related to the heart, showing a medical or physiological usage of the term.