There are 11 words that start with 'illega'.
| illegal | illegals | 
| illegally | illegality | 
| illegalize | illegalized | 
| illegalizes | illegalities | 
| illegalizing | illegalization | 
| illegalizations | |
Note: These 11 words that start with 'illega' are found from the USA & Canada version of the tournament Scrabble word list.