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.

Example Input: Sentence1: Similarly, stars are referred to as suns, but our star is the Sun. 
Sentence2: our star causes water to evaporate more quickly by adding heat.
Example Output: our

Example Input: Sentence1: Fission is a type of reproduction, but a baby is the result of sexual reproduction. 
Sentence2: the fallopian tubes are used to make babies.
Example Output: baby

Example Input: Sentence1: a plant requires water to grow. 
Sentence2: a plant requires Clouds to grow.
Example Output:
a