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: Rivers, rainwater, well water and most lakes contain fresh water. 
Sentence2: canyons are formed by rainwater.
[EX A]: rainwater

[EX Q]: Sentence1: Muscles can only contract. 
Sentence2: Contraction is a type of movement.
[EX A]: contract

[EX Q]: Sentence1: Cynodonts became more mammal-like as they continued to evolve. 
Sentence2: Synapsids were a further evolution in a chain of mammal-like animals.
[EX A]:
evolve