TASK DEFINITION: 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.
PROBLEM: Sentence1: Plants exhibit phototropism, or growing toward a light source. 
Sentence2: Phototropism means growing toward the energy of light.

SOLUTION: phototropism

PROBLEM: Sentence1: condensing causes a liquid to form. 
Sentence2: Air carries moisture that causes a liquid to form.

SOLUTION: causes

PROBLEM: Sentence1: When an atom or molecule is no longer neutral it is called an ion . 
Sentence2: if an atom loses an electron then it forms an ion.

SOLUTION:
ion