There are 12 words that start with 'synta'.
| syntax | syntagm | 
| syntagma | syntagms | 
| syntaxes | syntactic | 
| syntagmas | syntactics | 
| syntagmata | syntactical | 
| syntagmatic | syntactically | 
Note: These 12 words that start with 'synta' are found from the USA & Canada version of the tournament Scrabble word list.