This is the 16640th most frequent Russian word.
сердечно
"Сердечно" means "heartily" or "sincerely."
In this sentence, 'сердечно' is used as an adverb to express sincere gratitude with warmth and a tender heart.
Я сердечно благодарю вас за помощь.
I heartfully thank you for your help.
Here, 'сердечно' modifies the act of laughing, indicating it was done with full-hearted joy.
Она сердечно рассмеялась, услышав анекдот.
She laughed heartily upon hearing the joke.
In this instance, 'сердечно' describes the welcoming sentiment, emphasizing sincerity and warmth.