Es gibt ja so einige deutsche Woerter die auch im Englischen verwendet werden. Das hier ist mir aber neu.
“To study the behavior of a function in the neighborhood of the point x=0 we make the ansatz¹”
¹Anm: This German word cannot be correctly translated, which is why it has become customary to use it in the mathematics and physics literature. It means we just try something out (, in this case the particular way of writing the function locally, and see what this leads to.)