As others have said here, it is the abbreviation for 'ounces'....if you were concerned with the quality of a fragrance, perfume is the most concentrated fragrance, then toilet water, then cologne...Perfume is the most expensive, then followed in price range by toilet water, then cologne....also, buying what is called the 'splash' is a little less expensive (as in. Chanel No. 5 Splash)than a spray fragrance, as the spray fragrance is a little more expensive to produce because of the little hickey that sprays, whereas the 'splash' is just the fragrance itself in a bottle, to be used right out of the bottle or transferred (the best way, I think!) into a small, purse size spray container.....hope this helps!!!