What does the big ‘2’ in 2O2 mean?

I believe it means two molecules of oxygen.

Explanation:

The name for the molecular oxygen model is o2 and when you place a number in front of the element, it tells how many molecules there are of that element.  In this case, there are two molecules.

I would like to apologise in advance if this was incorrect.    

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

i think? ?