It appears from the study of hydronyms (river and lake names) that Baltic languages once predominated much farther eastwards and southwards than their modern confinement to the southeastern shores of the Baltic sea, and included regions that later became predominantly Slavic-speaking. The zone of Baltic hydronyms extends along the Baltic coast from the mouth of the Oder as far as Riga, eastwards as far as the line Yaroslavl–Moscow–Kursk and southwards as far as the line Oder mouth–Warsaw–Kyiv–Kursk: it thus includes much of northern and eastern Poland, Belarus and central European Russia.(fig. 2)