Detailed Instructions: 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: Ejaculation occurs when muscle contractions propel sperm from the epididymes. 
Sentence2: Ejaculation occurs when muscle contractions propel male gametes.
A:
Ejaculation