Final answer:
The unspent amount of $22 in the family's food budget for March is considered a surplus since they spent less than what was planned.
Step-by-step explanation:
If a family planned to spend $370 for food during March but only spent $348, the difference of $22 would be referred to as a surplus.
A surplus in budgeting terms means that less was spent than what was allotted or anticipated for that category in the budget. In contrast, a deficit occurs when more is spent than what was planned, leading to a shortfall. Therefore, since the family spent less than they planned, they have a surplus of funds which could potentially be saved or reallocated to other expenses or savings goals.