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: a stopwatch is used to measure time. 
Sentence2: Time can be measured with a clock or watch.

A: measure
****
Q: Sentence1: dew is formed when water vapor condenses over night. 
Sentence2: Condensing is a gas turning into a liquid.

A: condenses
****
Q: Sentence1: And, of course, the Sun is a star. 
Sentence2: if the Sun collapses it can form a black hole.

A:
Sun
****