Occurring by chance in a way that is fortunate or beneficial; lucky. It was a happy coincidence that they met at the airport.
He is happy to help with the project if needed.
Feeling or showing pleasure, contentment, or joy. She looks happy today.
Satisfied or pleased with a particular situation or outcome. I'm happy with the final design.
Giving pleasure or enjoyable. We spent many happy hours together.
(of words, a choice, or an action) apt, suitable, or well-judged; felicitous. That was a happy choice of words.