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: Plants exhibit phototropism, or growing toward a light source. 
Sentence2: Phototropism means growing toward the energy of light.
[A]: phototropism


[Q]: Sentence1: Rivers, rainwater, well water and most lakes contain fresh water. 
Sentence2: canyons are formed by rainwater.
[A]: rainwater


[Q]: Sentence1: Insects and hummingbirds are the primary pollinators. 
Sentence2: Hummingbirds increase plants genetic diversity.
[A]:
hummingbirds