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: creating wood-free paper does not require cutting down trees.
Sentence2: creating printed media requires cutting down trees.
[A]: creating

[Q]: Sentence1: natural magnetism is used for pointing north by a compass.
Sentence2: fields make compasses point north.
[A]:
compass