There are 17 words that start with 'happ'.
| happy | happed |
| happen | happens |
| happier | happily |
| happing | happened |
| happiest | happening |
| happiness | happenings |
| happinesses | happenchance |
| happenstance | happenchances |
| happenstances | |
Note: These 17 words that start with 'happ' are found from the USA & Canada version of the tournament Scrabble word list.