1 There are two types of glial cells in the nervous system: the large-bodied macroglia and the smaller microglia. 2  There are two classes of macroglia in the central nervous system: astrocytes and oligodendrocytes.
Exports directly contribute and imports directly reduce their nation's balance of trade (i.e. net exports). A trade surplus is positive net balance of trade, and a trade deficit is a negative net balance of trade.
trade. 1  the act or process of buying, selling, or exchanging commodities, at either wholesale or retail, within a country or between countries: domestic trade; foreign trade. 2  the act of buying, selling, or exchanging stocks, bonds, or currency: Stock brokerages typically charge a commission per trade. 3  a purchase or sale; business deal or transaction.