General happiness:
* Joyful
* Cheerful
* Delighted
* Glad
* Merry
* Content
* Pleased
* Elated
* Euphoric
* Blissful
Happiness from specific causes:
* Excited: A feeling of anticipation or eagerness.
* Thrilled: A strong sense of excitement and pleasure.
* Gratified: Feeling satisfied or pleased.
* Fulfilled: Feeling a sense of completion and satisfaction.
* Proud: Feeling a sense of accomplishment and self-worth.
* Relieved: Feeling a release from worry or stress.
* Hopeful: Feeling optimistic and positive about the future.
Positive emotional states:
* Optimistic: Seeing the good side of things.
* Positive: Having a good outlook.
* Enthusiastic: Full of energy and excitement.
* Peaceful: Feeling calm and at ease.
* Serene: Feeling tranquil and at peace.
* Content: Feeling satisfied and at ease.
Informal words:
* Tickled pink: Very pleased.
* Over the moon: Extremely happy.
* In seventh heaven: Very happy.
* On cloud nine: Very happy and carefree.
The best word to use will depend on the specific context and the nuance you want to convey.