IPA: /ˈmɛr.i.nəs/
KK: /ˈmɛrɪnəs/
The quality or state of being cheerful and full of joy.
The room was filled with merriness during the holiday celebration.
Merriness → It is formed from "merry" (from Old English *myrge*, meaning pleasant or joyful) and "-ness" (meaning the state or quality of). The word "merriness" refers to the state of being joyful or cheerful.
Think of the word 'merry' which means joyful, and remember that 'merriness' describes the state of being joyful.