There are 15 12-letter words that start with 'deca'.
| decalcifying | decalcomania | decantations | 
| decapitating | decapitation | decapitators | 
| decarbonated | decarbonates | decarbonized | 
| decarbonizer | decarbonizes | decarburized | 
| decarburizes | decasyllabic | decasyllable | 
Note: These 15 12-letter words that start with 'deca' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with decar, decal, decap, decam, decan, decad, decay, decag, decas, decat, decaf, decah.
5-letter words start with 'deca' (3)