There are 12 15-letter words that start with 'ar'.
| arbitrarinesses | archaebacterium |
| archaeopteryxes | archiepiscopate |
| architecturally | argumentatively |
| ariboflavinoses | ariboflavinosis |
| aromatherapists | arrondissements |
| arteriographies | artificialities |
Note: These 12 15-letter words that start with 'ar' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with arc, art, arr, arm, arb, arg, ari, ara, are, aro, ars, ard, arp, aru, ary, arn, ark, arh, arv, arf, arq, arl.
3-letter words start with 'ar' (8)