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: Pregnancy is the carrying of one or more offspring from fertilization until birth. 
Sentence2: An elephant carries their offspring from fertilization until birth, 22 months later.

A: fertilization
****
Q: Sentence1: a warm front causes cloudy and rainy weather. 
Sentence2: Stratus clouds are associated with a warm front.

A: front
****
Q: Sentence1: astronauts require preserved food for extended flights. 
Sentence2: An astronaut is a scientist who is a space explorer.

A:
astronauts
****