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: Streams may start with runoff or water seeping out of a spring.
Sentence2: Most water comes from precipitation.

A: water
****
Q: Sentence1: Sperm pass out of the body through the urethra.
Sentence2: Sperm travel from the testicles through the vas deferens to the seminal vesicles and the prostate.

A: Sperm
****
Q: Sentence1: Playing is just one of many ways that mammals and other animals learn how to behave.
Sentence2: Playing is one of many ways animal improve ability to survive and thrive.

A:
Playing
****