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: freezing means changing from a liquid into a solid by reducing heat energy. 
Sentence2: Water freezes into ice when cooled.

A: freezing
****
Q: Sentence1: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Sentence2: Fossils are the remains of prehistoric life.

A: fossils
****
Q: Sentence1: Invertebrates are animals that lack a vertebral column, or backbone. 
Sentence2: Millipedes, spiders and other invertebrates are probably taken as well.

A:
Invertebrates
****