The Vikings contributed to the modern English language, the modern taxing system, battle-ready military operations and the creation of currency to trade for goods instead of a bartering system. Some of these contributions were direct while others were a result of the Vikings' many attacks.
Modern English has incorporated French, Latin and Norse words into the language. Some of the Norse words used today include window, gang, angry, flaw and thrust. Language is one of the most significant contributions the Vikings made to history.
The modern concept of taxes came about as a result of Viking raids and threats. The Vikings killed many people when they attacked the European countries, causing kings and governments to raise money through taxes to fight them or pay their ransoms. This also caused the European governments to develop an organized military structure that could fight at any given moment against the Vikings' surprise attacks.
The Vikings helped to spread the idea of commerce in western Europe after doing business with the wealthy Arab Caliphate. Arab merchants in Russia used silver coins to buy goods from the Vikings which they then circulated throughout western European countries that were gold and silver poor. This changed the way Western commerce was conducted forever.