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.

Sentence1: Fish are the first known true chordates. 
Sentence2: Fish are the first known animal with a backbone.
Fish

Sentence1: hiding can be used for avoiding predators. 
Sentence2: Camouflage is used for avoiding predators.
avoiding

Sentence1: unequal heating of Earth 's surface by the Sun causes global wind patterns. 
Sentence2: Differences in temperature between the equatorial regions and higher latitudes om the Earth shapes global wind patterns.

Earth