Negative of a Game
In CGT, the negative, -G, of a game, G, is formed by giving each of the two players the negatives of the options of the other one.
To form the negative of a go position, we simply reverse the colors of the stones. Plainly, the options available to Black in the original position have corresponding options for White in the reversed position, and vice versa. And since scores for White are the negative of scores for Black, these corresponding options are the negatives of the originals.
See Difference Game.