Definition: 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.
Input: Sentence1: Dates are provided for the recognized eras and periods of geologic time. 
Sentence2: Macroevolution above the level of the species is evolution over eras and periods.

eras