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.

[EX Q]: Sentence1: gills are used for breathing water by aquatic animals. 
Sentence2: gills are used for breathing water by sharks.
[EX A]: are

[EX Q]: Sentence1: Viruses are parasites of cells. 
Sentence2: Populations of viruses do not grow through division because they are parasites.
[EX A]: are

[EX Q]: Sentence1: Roots have primary and secondary meristems for growth in length and width. 
Sentence2: Size is measured by width and length.
[EX A]:
length