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: Amphibians have permeable skin that easily absorbs substances from the environment. 
Sentence2: Some substances are harmful to the body and block biological systems.
[A]: substances


[Q]: Sentence1: Mitosis is cell division. 
Sentence2: mitosis often causes growth.
[A]: Mitosis


[Q]: Sentence1: melting is when solids are heated above their melting point. 
Sentence2: Thulium melts above 1545 Celsius.
[A]:
melting