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: Sound vibrations can be compared to pond ripples. 
Sentence2: dropping an object into water causes pond ripples.
[EX A]: pond

[EX Q]: Sentence1: Flatworms Flatworms or Platyhelminthes include flukes, tapeworms, and turbellarians. 
Sentence2: Tapeworms belong to the phylum Platyhelminthes.
[EX A]: tapeworms

[EX Q]: Sentence1: Mating is generally preceded by courtship. 
Sentence2: Mating is generally similar across species.
[EX A]:
Mating