Further should be used when extending your point from a previous argument already made. Furthermore should be used when you’re introducing a new argument. Further is used in the middle of a sentence, while furthermore is used at the start of a sentence.

comparative of far : to a greater distance or degree, or at a more advanced level: I never got further than the first five pages of "Ulysses". get further We discussed the problem but we didn't get much further in actually solving it. The whole matter is further complicated by the fact that Amanda and Jo refuse to speak to each other.

Definition of Further to promote or advance forward Examples of Further in a sentence As a way to further her career, the manager took business classes at the local night school. The teacher tried to further the students’ understanding of the material by giving them extra help with difficult problems.