-ness (state of being)
-ness
Makes a noun: the state of being something.
We thanked our neighbour for her kindness.
Kindness
Being kind and caring.
Small acts of kindness make a classroom happy.
Happiness
The feeling of being happy.
The children's happiness showed on their faces at the fair.
Remember: Keep every letter: mean + ness = meanness, sudden + ness = suddenness (double n). But y → i: happy → happiness.