A river rising in central Argentina and flowing about 644 km (400 mi) eastward to the Atlantic Ocean.
A river rising in southern Brazil and flowing about 805 km (500 mi) generally southwest to the Uruguay River in central Uruguay.
A river of northwest South America flowing about 2,253 km (1,400 mi) from eastern Colombia to the Amazon River near Manaus, Brazil. Part of its course forms a section of the Colombia-Venezuela border.
(nā'grō, ně'grō, -grŏŏ) 