Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

[Q]: Sentence1: a circle graph can be used to display percents. 
Sentence2: pie charts are circle graphs.
[A]: circle


[Q]: Sentence1: All oaks are trees. 
Sentence2: Cutting down oaks has a negative impact on an ecosystem.
[A]: oaks


[Q]: Sentence1: when a river floods , that river deposits soil in flood plains. 
Sentence2: plains get soil from floods.
[A]:
plains