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.

Ex Input:
Sentence1: air pollution can cause the pH of soil to decrease. 
Sentence2: Acidity is measured with a pH meter or with pH paper strips.

Ex Output:
pH


Ex Input:
Sentence1: an image in a mirror is formed by reflecting light. 
Sentence2: mirrors can be seen with our eyes.

Ex Output:
mirror


Ex Input:
Sentence1: Endocrine hormones travel throughout the body in the blood. 
Sentence2: Endocrine hormones travel through the body in something that runs like water.

Ex Output:

Endocrine