Variable costs are a little different and allow you some budgeting flexibility. These are costs that fluctuate directly with the amount of business you support. Variable costs—costs that are business-dependent—include supply of goods and materials and, to some degree, part-time labor necessary to keep the business operating apace with demand.
Semi-variable costs are expenses with components that are fixed and components that are variable. For example, telephone expenses are semi-variable costs in that the monthly service charge is fixed and the charges for long-distance calls and the 800 number are variable.