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: Mutations are essential for evolution to occur. 
Sentence2: Genes are altered for evolution to occur.

A: evolution
****
Q: Sentence1: a camera is used for recording images. 
Sentence2: a camera is used for recording binary.

A: camera
****
Q: Sentence1: Glucose is used for energy by the cells of most organisms. 
Sentence2: Glucose metabolism relates to how cells use or store glucose.

A:
cells
****