The ac is a prefix in a set of prefixs with the same rule, the letter a plus a consonant which ... is the first letter of a root, other examples: ab-,ac-,ad-,af-,ag-,an-,ap-,ar-,as-,at. One ... of the meanings of the prefix is specify the direction of the root, for example: to, near, toward ... . [accord: ac(to) + cord(heart)] Accord means agreement, be in harmony, reconcile , be of one mind