There are 17 words that start with 'behav'.
| behave | behaved | 
| behaver | behaves | 
| behavers | behaving | 
| behavior | behaviors | 
| behaviour | behavioral | 
| behaviours | behaviorism | 
| behaviorist | behaviorally | 
| behaviorisms | behaviorists | 
| behavioristic | |
Note: These 17 words that start with 'behav' are found from the USA & Canada version of the tournament Scrabble word list.