Base year: is a certain fixed year against which percentage of changes of indices are compared The index for the base year is equal to 100.

Classification of groups for goods and services: goods and services subject to indices are classified according to their intrinsic nature and international classifications as well as national requirements. However, the overall bases of classifications are those recommended by the United Nations (i.e, the SNA[1] for consumer index for goods and services, the SITC[2] for wholesale trade, and ISIC[3] Rev. 3 for producer) and modified with respect to the economy considerations of Iran.

Consumer price index (CPI): is a measure of changes over the base year in prices of a certain fixed number of goods and services consumed by households.

Price index for exported commodities: measures changes in goods prices exported. Exported commodities include all commodities which are completely produced inside the country or exported as semi-finished goods or raw material.

Producer price index (PPI): shows the trend of changes in prices paid by producers in different economic sectors such as agriculture, fishing, manufacturing, mining and services. Producer price refers to the price which the purchaser pays to the producer for purchasing each commodity; it also represents the selling price of goods or services produced and supplied to wholesalers, domestic retail sellers and other industries and/or exported to foreign countries.

Weight:   contribution   of   any   single good or service to the set of goods and services subject to indices is called "weight". In consumer price indices for goods and services, contribution of any single good or service equals to a proportion of expenditure spent by a household to the total household expenditure. In wholesale price index, contribution of any single good is equal to selling value of wholesale of goods to the total value of wholesale of goods. In producer price index, contribution of any single good or service is equal to proportion of the production value or selling value of a single good/service to the production or selling value of the set of goods and services.

Wholesale price index for goods: is a measure of changes in wholesale prices of goods over the base year.