In German linguistics, the Sankt Goar line, German: das–dat line, or German: was–wat line is an isogloss separating the dialects to the north, which have a t in the words German: dat (English that) and German: wat (English what), from the dialects to the south (including standard German), which have an s: German: das, was. The line runs from North-East to South-West and crosses the river Rhine at the town of Sankt Goar.