a loss only in the paper in a tax return and has no relationship to an economic profit or loss

a very real loss

Based on a comparison of current market price to original cost, paper loss is the difference between the net cost of a security and the net sale price, if that security were to be sold at its current price (assuming that price is lower than what the buyer paid for it).

How investors fool themselves into thinking they haven't lost money yet. "It isn't a loss until you sell." Face it, if you buy a stock at $25 and now it is $15, you lost money.