Besides being the main currency of the United States , the American dollar is used as the standard unit of currency in international markets for commodities such as gold and petroleum ( the latter , sometimes called petrocurrency , is the source of the term petrodollar ) .
SCONJ VERB DET ADJ NOUN ADP DET PROPN PROPN , DET ADJ NOUN AUX VERB ADP DET ADJ NOUN ADP NOUN ADP ADJ NOUN ADP NOUN ADJ ADP NOUN CCONJ NOUN ( DET ADJ , ADV VERB NOUN , AUX DET NOUN ADP DET NOUN ADJ ) .