The balance of trade (or net exports, sometimes symbolized as NX) is the difference between the monetary value of exports and imports of output in an economy over a certain period. It is the relationship between a nation's imports and exports. A favourable balance of trade is known as a trade surplus and consists of exporting more than is imported; an unfavourable balance of trade is known as a trade deficit or, informally, a trade gap. The balance of trade is sometimes divided into a goods and a services balance.