Happiness expression is an expression that is used to say that someone or people are glad have excited feelings.

expressing happyness :
-I'm happy
-terrific
-i'm (very) pleased/dilighted (about) .....
-i can't say how pleased/dilighted i'm about it......
-great
-fantastic
-etc.

Example :
I'm Very happy because how I can get together with my old friend.Oh...... how I miss them. I see that their appearances have not changet. Dikta, the winner of piano competition, is playing us romantic music.