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: a light bulb is used for seeing in the dark. 
Sentence2: light is required for seeing.
seeing

Sentence1: Antibodies are large, Y-shaped proteins that recognize and bind to antigens. 
Sentence2: Some of the antibodies, antophospholipid antibodies, cause blood clots.
Antibodies

Sentence1: Bacteria are very small. 
Sentence2: microscope is used to see bacteria by biologists by making them appear bigger.

Bacteria