National parkA national park is a natural park in use for conservation purposes, created and protected by national governments. Often it is a reserve of natural, semi-natural, or developed land that a government declares or owns. Although individual countries designate their own national parks differently, there is a common idea: the conservation of 'wild nature' for posterity and as a symbol of national pride. National parks are almost always open to visitors.
Stock and flowEconomics, business, accounting, and related fields often distinguish between quantities that are stocks and those that are flows. These differ in their units of measurement. A stock is measured at one specific time, and represents a quantity existing at that point in time (say, December 31, 2004), which may have accumulated in the past. A flow variable is measured over an interval of time. Therefore, a flow would be measured per unit of time (say a year). Flow is roughly analogous to rate or speed in this sense.
Asset classesIn finance, an asset class is a group of financial instruments that have similar financial characteristics and behave similarly in the marketplace. We can often break these instruments into those having to do with real assets and those having to do with financial assets. Often, assets within the same asset class are subject to the same laws and regulations; however, this is not always true. For instance, futures on an asset are often considered part of the same asset class as the underlying instrument but are subject to different regulations than the underlying instrument.
