A budget is a calculation play, usually but not always financial, for a defined period, often one year or a month. A budget may include anticipated sales volumes and revenues, resource quantities including time, costs and expenses, environmental impacts such as greenhouse gas emissions, other impacts, assets, liabilities and cash flows. Companies, governments, families, and other organizations use budgets to express strategic plans of activities in measurable terms. A budget expresses intended expenditures along with proposals for how to meet them with resources. A budget may express a surplus, providing resources for use at a future time, or a deficit in which expenditures exceed income or other resources.