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.

Sentence1: creating paper requires cutting down trees. 
Sentence2: Trees begin as epiphytes on host trees.
trees

Sentence1: erosion of soil has a negative impact on the environment. 
Sentence2: erosion of soil has a negative impact on forests.
erosion

Sentence1: Water, for example, is a liquid. 
Sentence2: beads of liquid are formed by vapor condensing.

liquid