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: Rainy clouds cause rain, and excess water vapor from clouds is the basis of rainbows. 
Sentence2: Condensation can lead to rain.
[A]: rain


[Q]: Sentence1: Many corals secrete an exoskeleton that builds up to become a coral reef. 
Sentence2: Good examples are Bubble coral, Elegance coral, Frogspawn and other Euphyllia corals.
[A]: coral


[Q]: Sentence1: Bivalves feed on plankton and nonliving organic matter. 
Sentence2: Molluscs feed on plankton and nonliving organic matter.
[A]:
feed