In German linguistics, the Sankt Goar line, line, or line is an isogloss in Europe in the areas of Belgium, Germany and Luxembourg. It separates the dialects to the north, which have a t in the words (English that) and (English what), from the dialects to the south (including standard German), which have an s: . The line runs from North-East to South-West and crosses the river Rhine at the town of Sankt Goar.