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: a solution is formed by one substance being dissolved in another substance. 
Sentence2: A solution is formed when limestone is dissolved in ocean water.
formed

Sentence1: Without the pollinated seeds there are no hormones. 
Sentence2: if flowers did not attract pollinators there would be no hormones.

hormones