This is the 4340th most frequent Russian word.
благодарности
"Gratitude" or "thanks."
Here, 'благодарности' is used as a plural noun in the context of expressing thanks.
Я хочу выразить свои благодарности вашему учителю.
I want to express my gratitude to your teacher.
In this sentence, 'благодарности' is part of an idiomatic expression 'в знак благодарности,' meaning 'as a sign of gratitude.'
В знак благодарности он подарил ей букет цветов.
As a sign of gratitude, he gifted her a bouquet of flowers.
Here, 'благодарностей' emphasizes the plural form to indicate multiple acts or forms of gratitude within the letter.