This is the 117th most frequent Spanish word.
muchas
"Many" or "a lot of."
In this sentence, 'muchas' (many) indicates the intensity of gratitude, intensifying 'gracias' (thanks).
Muchas gracias por tu ayuda.
Thank you very much for your help.
Here, 'muchas' (many) quantifies the noun 'invitaciones' (invitations), showing that the count is plural and ample.
Tengo muchas invitaciones para la fiesta.
I have many invitations for the party.
In this sentence, 'muchas' (many) emphasizes the quantity of 'personas' (people), conveying that it is a considerable number.