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: Most soil nutrients are cations. 
Sentence2: decomposition increases the amount of cations in the soil.
Example Output: cations

Example Input: Sentence1: an automobile engine transforms chemical energy into mechanical energy. 
Sentence2: cars transform chemical energy into mechanical energy.
Example Output: chemical

Example Input: Sentence1: Puberty is the period during which humans become sexually mature. 
Sentence2: If blood sugar control is good during puberty, full growth is usually reached.
Example Output:
Puberty